<!doctype html><html lang="en">
 <head>
  <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
  <title>加速的图形识别</title>
  <meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
<style data-fill-with="stylesheet">/******************************************************************************
 *                   Style sheet for the W3C specifications                   *
 *
 * Special classes handled by this style sheet include:
 *
 * Indices
 *   - .toc for the Table of Contents (<ol class="toc">)
 *     + <span class="secno"> for the section numbers
 *   - #toc for the Table of Contents (<nav id="toc">)
 *   - ul.index for Indices (<a href="#ref">term</a><span>, in §N.M</span>)
 *   - table.index for Index Tables (e.g. for properties or elements)
 *
 * Structural Markup
 *   - table.data for general data tables
 *     -> use 'scope' attribute, <colgroup>, <thead>, and <tbody> for best results !
 *     -> use <table class='complex data'> for extra-complex tables
 *     -> use <td class='long'> for paragraph-length cell content
 *     -> use <td class='pre'> when manual line breaks/indentation would help readability
 *   - dl.switch for switch statements
 *   - ol.algorithm for algorithms (helps to visualize nesting)
 *   - .figure and .caption (HTML4) and figure and figcaption (HTML5)
 *     -> .sidefigure for right-floated figures
 *   - ins/del
 *
 * Code
 *   - pre and code
 *
 * Special Sections
 *   - .note       for informative notes             (div, p, span, aside, details)
 *   - .example    for informative examples          (div, p, pre, span)
 *   - .issue      for issues                        (div, p, span)
 *   - .assertion  for assertions                    (div, p, span)
 *   - .advisement for loud normative statements     (div, p, strong)
 *   - .annoying-warning for spec obsoletion notices (div, aside, details)
 *
 * Definition Boxes
 *   - pre.def   for WebIDL definitions
 *   - table.def for tables that define other entities (e.g. CSS properties)
 *   - dl.def    for definition lists that define other entitles (e.g. HTML elements)
 *
 * Numbering
 *   - .secno for section numbers in .toc and headings (<span class='secno'>3.2</span>)
 *   - .marker for source-inserted example/figure/issue numbers (<span class='marker'>Issue 4</span>)
 *   - ::before styled for CSS-generated issue/example/figure numbers:
 *     -> Documents wishing to use this only need to add
 *        figcaption::before,
 *        .caption::before { content: "Figure "  counter(figure) " ";  }
 *        .example::before { content: "Example " counter(example) " "; }
 *        .issue::before   { content: "Issue "   counter(issue) " ";   }
 *
 * Header Stuff (ignore, just don't conflict with these classes)
 *   - .head for the header
 *   - .copyright for the copyright
 *
 * Miscellaneous
 *   - .overlarge for things that should be as wide as possible, even if
 *     that overflows the body text area. This can be used on an item or
 *     on its container, depending on the effect desired.
 *     Note that this styling basically doesn't help at all when printing,
 *     since A4 paper isn't much wider than the max-width here.
 *     It's better to design things to fit into a narrower measure if possible.
 *   - js-added ToC jump links (see fixup.js)
 *
 ******************************************************************************/

/******************************************************************************/
/*                                   Body                                     */
/******************************************************************************/

	body {
		counter-reset: example figure issue;

		/* Layout */
		max-width: 50em;               /* limit line length to 50em for readability   */
		margin: 0 auto;                /* center text within page                     */
		padding: 1.6em 1.5em 2em 50px; /* assume 16px font size for downlevel clients */
		padding: 1.6em 1.5em 2em calc(26px + 1.5em); /* leave space for status flag     */

		/* Typography */
		line-height: 1.5;
		font-family: sans-serif;
		widows: 2;
		orphans: 2;
		word-wrap: break-word;
		overflow-wrap: break-word;
		hyphens: auto;

		/* Colors */
		color: black;
		background: white top left fixed no-repeat;
		background-size: 25px auto;
	}


/******************************************************************************/
/*                         Front Matter & Navigation                          */
/******************************************************************************/

/** Header ********************************************************************/

	div.head { margin-bottom: 1em }
	div.head hr { border-style: solid; }

	div.head h1 {
		font-weight: bold;
		margin: 0 0 .1em;
		font-size: 220%;
	}

	div.head h2 { margin-bottom: 1.5em;}

/** W3C Logo ******************************************************************/

	.head .logo {
		float: right;
		margin: 0.4rem 0 0.2rem .4rem;
	}

	.head img[src*="logos/W3C"] {
		display: block;
		border: solid #1a5e9a;
		border-width: .65rem .7rem .6rem;
		border-radius: .4rem;
		background: #1a5e9a;
		color: white;
		font-weight: bold;
	}

	.head a:hover > img[src*="logos/W3C"],
	.head a:focus > img[src*="logos/W3C"] {
		opacity: .8;
	}

	.head a:active > img[src*="logos/W3C"] {
		background: #c00;
		border-color: #c00;
	}

	/* see also additional rules in Link Styling section */

/** Copyright *****************************************************************/

	p.copyright,
	p.copyright small { font-size: small }

/** Back to Top / ToC Toggle **************************************************/

	@media print {
		#toc-nav {
			display: none;
		}
	}
	@media not print {
		#toc-nav {
			position: fixed;
			z-index: 2;
			bottom: 0; left: 0;
			margin: 0;
			min-width: 1.33em;
			border-top-right-radius: 2rem;
			box-shadow: 0 0 2px;
			font-size: 1.5em;
			color: black;
		}
		#toc-nav > a {
			display: block;
			white-space: nowrap;

			height: 1.33em;
			padding: .1em 0.3em;
			margin: 0;

			background: white;
			box-shadow: 0 0 2px;
			border: none;
			border-top-right-radius: 1.33em;
			background: white;
		}
		#toc-nav > #toc-jump {
			padding-bottom: 2em;
			margin-bottom: -1.9em;
		}

		#toc-nav > a:hover,
		#toc-nav > a:focus {
			background: #f8f8f8;
		}
		#toc-nav > a:not(:hover):not(:focus) {
			color: #707070;
		}

		/* statusbar gets in the way on keyboard focus; remove once browsers fix */
		#toc-nav > a[href="#toc"]:not(:hover):focus:last-child {
			padding-bottom: 1.5rem;
		}

		#toc-nav:not(:hover) > a:not(:focus) > span + span {
			/* Ideally this uses :focus-within on #toc-nav */
			display: none;
		}
		#toc-nav > a > span + span {
			padding-right: 0.2em;
		}

		#toc-toggle-inline {
			vertical-align: 0.05em;
			font-size: 80%;
			color: gray;
			color: hsla(203,20%,40%,.7);
			border-style: none;
			background: transparent;
			position: relative;
		}
		#toc-toggle-inline:hover:not(:active),
		#toc-toggle-inline:focus:not(:active) {
			text-shadow: 1px 1px silver;
			top: -1px;
			left: -1px;
		}

		#toc-nav :active {
			color: #C00;
		}
	}

/** ToC Sidebar ***************************************************************/

	/* Floating sidebar */
	@media screen {
		body.toc-sidebar #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			max-width: 80%;
			max-width: calc(100% - 2em - 26px);
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			background: inherit;
			background-color: #f7f8f9;
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
		}
		body.toc-sidebar #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
		}
		body.toc-sidebar #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	/* Hide main scroller when only the ToC is visible anyway */
	@media screen and (max-width: 28em) {
		body.toc-sidebar {
			overflow: hidden;
		}
	}

	/* Sidebar with its own space */
	@media screen and (min-width: 78em) {
		body:not(.toc-inline) #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			background: inherit;
			background-color: #f7f8f9;
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
		}
		body:not(.toc-inline) #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
		}

		body:not(.toc-inline) {
			padding-left: 29em;
		}
		/* See also Overflow section at the bottom */

		body:not(.toc-inline) #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	@media screen and (min-width: 90em) {
		body:not(.toc-inline) {
			margin: 0 4em;
		}
	}

/******************************************************************************/
/*                                Sectioning                                  */
/******************************************************************************/

/** Headings ******************************************************************/

	h1, h2, h3, h4, h5, h6, dt {
		page-break-after: avoid;
		page-break-inside: avoid;
		font: 100% sans-serif;   /* Reset all font styling to clear out UA styles */
		font-family: inherit;    /* Inherit the font family. */
		line-height: 1.2;        /* Keep wrapped headings compact */
		hyphens: manual;         /* Hyphenated headings look weird */
	}

	h2, h3, h4, h5, h6 {
		margin-top: 3rem;
	}

	h1, h2, h3 {
		color: #005A9C;
		background: transparent;
	}

	h1 { font-size: 170%; }
	h2 { font-size: 140%; }
	h3 { font-size: 120%; }
	h4 { font-weight: bold; }
	h5 { font-style: italic; }
	h6 { font-variant: small-caps; }
	dt { font-weight: bold; }

/** Subheadings ***************************************************************/

	h1 + h2,
	#subtitle {
		/* #subtitle is a subtitle in an H2 under the H1 */
		margin-top: 0;
	}
	h2 + h3,
	h3 + h4,
	h4 + h5,
	h5 + h6 {
		margin-top: 1.2em; /* = 1 x line-height */
	}

/** Section divider ***********************************************************/

	:not(.head) > hr {
		font-size: 1.5em;
		text-align: center;
		margin: 1em auto;
		height: auto;
		border: transparent solid 0;
		background: transparent;
	}
	:not(.head) > hr::before {
		content: "\2727\2003\2003\2727\2003\2003\2727";
	}

/******************************************************************************/
/*                            Paragraphs and Lists                            */
/******************************************************************************/

	p {
		margin: 1em 0;
	}

	dd > p:first-child,
	li > p:first-child {
		margin-top: 0;
	}

	ul, ol {
		margin-left: 0;
		padding-left: 2em;
	}

	li {
		margin: 0.25em 0 0.5em;
		padding: 0;
	}

	dl dd {
		margin: 0 0 .5em 2em;
	}

	.head dd + dd { /* compact for header */
		margin-top: -.5em;
	}

	/* Style for algorithms */
	ol.algorithm ol:not(.algorithm),
	.algorithm > ol ol:not(.algorithm) {
	 border-left: 0.5em solid #DEF;
	}

	/* Put nice boxes around each algorithm. */
	[data-algorithm]:not(.heading) {
	  padding: .5em;
	  border: thin solid #ddd; border-radius: .5em;
	  margin: .5em calc(-0.5em - 1px);
	}
	[data-algorithm]:not(.heading) > :first-child {
	  margin-top: 0;
	}
	[data-algorithm]:not(.heading) > :last-child {
	  margin-bottom: 0;
	}

	/* Style for switch/case <dl>s */
	dl.switch > dd > ol.only,
	dl.switch > dd > .only > ol {
	 margin-left: 0;
	}
	dl.switch > dd > ol.algorithm,
	dl.switch > dd > .algorithm > ol {
	 margin-left: -2em;
	}
	dl.switch {
	 padding-left: 2em;
	}
	dl.switch > dt {
	 text-indent: -1.5em;
	 margin-top: 1em;
	}
	dl.switch > dt + dt {
	 margin-top: 0;
	}
	dl.switch > dt::before {
	 content: '\21AA';
	 padding: 0 0.5em 0 0;
	 display: inline-block;
	 width: 1em;
	 text-align: right;
	 line-height: 0.5em;
	}

/** Terminology Markup ********************************************************/


/******************************************************************************/
/*                                 Inline Markup                              */
/******************************************************************************/

/** Terminology Markup ********************************************************/
	dfn   { /* Defining instance */
		font-weight: bolder;
	}
	a > i { /* Instance of term */
		font-style: normal;
	}
	dt dfn code, code.idl {
		font-size: medium;
	}
	dfn var {
		font-style: normal;
	}

/** Change Marking ************************************************************/

	del { color: red;  text-decoration: line-through; }
	ins { color: #080; text-decoration: underline;    }

/** Miscellaneous improvements to inline formatting ***************************/

	sup {
		vertical-align: super;
		font-size: 80%
	}

/******************************************************************************/
/*                                    Code                                    */
/******************************************************************************/

/** General monospace/pre rules ***********************************************/

	pre, code, samp {
		font-family: Menlo, Consolas, "DejaVu Sans Mono", Monaco, monospace;
		font-size: .9em;
		page-break-inside: avoid;
		hyphens: none;
		text-transform: none;
	}
	pre code,
	code code {
		font-size: 100%;
	}

	pre {
		margin-top: 1em;
		margin-bottom: 1em;
		overflow: auto;
	}

/** Inline Code fragments *****************************************************/

  /* Do something nice. */

/******************************************************************************/
/*                                    Links                                   */
/******************************************************************************/

/** General Hyperlinks ********************************************************/

	/* We hyperlink a lot, so make it less intrusive */
	a[href] {
		color: #034575;
		text-decoration: none;
		border-bottom: 1px solid #707070;
		/* Need a bit of extending for it to look okay */
		padding: 0 1px 0;
		margin: 0 -1px 0;
	}
	a:visited {
		border-bottom-color: #BBB;
	}

	/* Use distinguishing colors when user is interacting with the link */
	a[href]:focus,
	a[href]:hover {
		background: #f8f8f8;
		background: rgba(75%, 75%, 75%, .25);
		border-bottom-width: 3px;
		margin-bottom: -2px;
	}
	a[href]:active {
		color: #C00;
		border-color: #C00;
	}

	/* Backout above styling for W3C logo */
	.head .logo,
	.head .logo a {
		border: none;
		text-decoration: none;
		background: transparent;
	}

/******************************************************************************/
/*                                    Images                                  */
/******************************************************************************/

	img {
		border-style: none;
	}

	/* For autogen numbers, add
	   .caption::before, figcaption::before { content: "Figure " counter(figure) ". "; }
	*/

	figure, .figure, .sidefigure {
		page-break-inside: avoid;
		text-align: center;
		margin: 2.5em 0;
	}
	.figure img,    .sidefigure img,    figure img,
	.figure object, .sidefigure object, figure object {
		max-width: 100%;
		margin: auto;
	}
	.figure pre, .sidefigure pre, figure pre {
		text-align: left;
		display: table;
		margin: 1em auto;
	}
	.figure table, figure table {
		margin: auto;
	}
	@media screen and (min-width: 20em) {
		.sidefigure {
			float: right;
			width: 50%;
			margin: 0 0 0.5em 0.5em
		}
	}
	.caption, figcaption, caption {
		font-style: italic;
		font-size: 90%;
	}
	.caption::before, figcaption::before, figcaption > .marker {
		font-weight: bold;
	}
	.caption, figcaption {
		counter-increment: figure;
	}

	/* DL list is indented 2em, but figure inside it is not */
	dd > .figure, dd > figure { margin-left: -2em }

/******************************************************************************/
/*                             Colored Boxes                                  */
/******************************************************************************/

	.issue, .note, .example, .assertion, .advisement, blockquote {
		padding: .5em;
		border: .5em;
		border-left-style: solid;
		page-break-inside: avoid;
	}
	span.issue, span.note {
		padding: .1em .5em .15em;
		border-right-style: solid;
	}

	.issue,
	.note,
	.example,
	.advisement,
	.assertion,
	blockquote {
		margin: 1em auto;
	}
	.note  > p:first-child,
	.issue > p:first-child,
	blockquote > :first-child {
		margin-top: 0;
	}
	blockquote > :last-child {
		margin-bottom: 0;
	}

/** Blockquotes ***************************************************************/

	blockquote {
		border-color: silver;
	}

/** Open issue ****************************************************************/

	.issue {
		border-color: #E05252;
		background: #FBE9E9;
		counter-increment: issue;
		overflow: auto;
	}
	.issue::before, .issue > .marker {
		text-transform: uppercase;
		color: #AE1E1E;
		padding-right: 1em;
		text-transform: uppercase;
	}
	/* Add .issue::before { content: "Issue " counter(issue) " "; } for autogen numbers,
	   or use class="marker" to mark up the issue number in source. */

/** Example *******************************************************************/

	.example {
		border-color: #E0CB52;
		background: #FCFAEE;
		counter-increment: example;
		overflow: auto;
		clear: both;
	}
	.example::before, .example > .marker {
		text-transform: uppercase;
		color: #827017;
		min-width: 7.5em;
		display: block;
	}
	/* Add .example::before { content: "Example " counter(example) " "; } for autogen numbers,
	   or use class="marker" to mark up the example number in source. */

/** Non-normative Note ********************************************************/

	.note {
		border-color: #52E052;
		background: #E9FBE9;
		overflow: auto;
	}

	.note::before, .note > .marker,
	details.note > summary::before,
	details.note > summary > .marker {
		text-transform: uppercase;
		display: block;
		color: hsl(120, 70%, 30%);
	}
	/* Add .note::before { content: "Note"; } for autogen label,
	   or use class="marker" to mark up the label in source. */

	details.note > summary {
		display: block;
		color: hsl(120, 70%, 30%);
	}
	details.note[open] > summary {
		border-bottom: 1px silver solid;
	}

/** Assertion Box *************************************************************/
	/*  for assertions in algorithms */

	.assertion {
		border-color: #AAA;
		background: #EEE;
	}

/** Advisement Box ************************************************************/
	/*  for attention-grabbing normative statements */

	.advisement {
		border-color: orange;
		border-style: none solid;
		background: #FFEECC;
	}
	strong.advisement {
		display: block;
		text-align: center;
	}
	.advisement > .marker {
		color: #B35F00;
	}

/** Spec Obsoletion Notice ****************************************************/
	/* obnoxious obsoletion notice for older/abandoned specs. */

	details {
		display: block;
	}
	summary {
		font-weight: bolder;
	}

	.annoying-warning:not(details),
	details.annoying-warning:not([open]) > summary,
	details.annoying-warning[open] {
		background: #fdd;
		color: red;
		font-weight: bold;
		padding: .75em 1em;
		border: thick red;
		border-style: solid;
		border-radius: 1em;
	}
	.annoying-warning :last-child {
		margin-bottom: 0;
	}

@media not print {
	details.annoying-warning[open] {
		position: fixed;
		left: 1em;
		right: 1em;
		bottom: 1em;
		z-index: 1000;
	}
}

	details.annoying-warning:not([open]) > summary {
		text-align: center;
	}

/** Entity Definition Boxes ***************************************************/

	.def {
		padding: .5em 1em;
		background: #DEF;
		margin: 1.2em 0;
		border-left: 0.5em solid #8CCBF2;
	}

/******************************************************************************/
/*                                    Tables                                  */
/******************************************************************************/

	th, td {
		text-align: left;
		text-align: start;
	}

/** Property/Descriptor Definition Tables *************************************/

	table.def {
		/* inherits .def box styling, see above */
		width: 100%;
		border-spacing: 0;
	}

	table.def td,
	table.def th {
		padding: 0.5em;
		vertical-align: baseline;
		border-bottom: 1px solid #bbd7e9;
	}

	table.def > tbody > tr:last-child th,
	table.def > tbody > tr:last-child td {
		border-bottom: 0;
	}

	table.def th {
		font-style: italic;
		font-weight: normal;
		padding-left: 1em;
		width: 3em;
	}

	/* For when values are extra-complex and need formatting for readability */
	table td.pre {
		white-space: pre-wrap;
	}

	/* A footnote at the bottom of a def table */
	table.def           td.footnote {
		padding-top: 0.6em;
	}
	table.def           td.footnote::before {
		content: " ";
		display: block;
		height: 0.6em;
		width: 4em;
		border-top: thin solid;
	}

/** Data tables (and properly marked-up index tables) *************************/
	/*
		 <table class="data"> highlights structural relationships in a table
		 when correct markup is used (e.g. thead/tbody, th vs. td, scope attribute)

		 Use class="complex data" for particularly complicated tables --
		 (This will draw more lines: busier, but clearer.)

		 Use class="long" on table cells with paragraph-like contents
		 (This will adjust text alignment accordingly.)
		 Alternately use class="longlastcol" on tables, to have the last column assume "long".
	*/

	table {
		word-wrap: normal;
		overflow-wrap: normal;
		hyphens: manual;
	}

	table.data,
	table.index {
		margin: 1em auto;
		border-collapse: collapse;
		border: hidden;
		width: 100%;
	}
	table.data caption,
	table.index caption {
		max-width: 50em;
		margin: 0 auto 1em;
	}

	table.data td,  table.data th,
	table.index td, table.index th {
		padding: 0.5em 1em;
		border-width: 1px;
		border-color: silver;
		border-top-style: solid;
	}

	table.data thead td:empty {
		padding: 0;
		border: 0;
	}

	table.data  thead,
	table.index thead,
	table.data  tbody,
	table.index tbody {
		border-bottom: 2px solid;
	}

	table.data colgroup,
	table.index colgroup {
		border-left: 2px solid;
	}

	table.data  tbody th:first-child,
	table.index tbody th:first-child  {
		border-right: 2px solid;
		border-top: 1px solid silver;
		padding-right: 1em;
	}

	table.data th[colspan],
	table.data td[colspan] {
		text-align: center;
	}

	table.complex.data th,
	table.complex.data td {
		border: 1px solid silver;
		text-align: center;
	}

	table.data.longlastcol td:last-child,
	table.data td.long {
	 vertical-align: baseline;
	 text-align: left;
	}

	table.data img {
		vertical-align: middle;
	}


/*
Alternate table alignment rules

	table.data,
	table.index {
		text-align: center;
	}

	table.data  thead th[scope="row"],
	table.index thead th[scope="row"] {
		text-align: right;
	}

	table.data  tbody th:first-child,
	table.index tbody th:first-child  {
		text-align: right;
	}

Possible extra rowspan handling

	table.data  tbody th[rowspan]:not([rowspan='1']),
	table.index tbody th[rowspan]:not([rowspan='1']),
	table.data  tbody td[rowspan]:not([rowspan='1']),
	table.index tbody td[rowspan]:not([rowspan='1']) {
		border-left: 1px solid silver;
	}

	table.data  tbody th[rowspan]:first-child,
	table.index tbody th[rowspan]:first-child,
	table.data  tbody td[rowspan]:first-child,
	table.index tbody td[rowspan]:first-child{
		border-left: 0;
		border-right: 1px solid silver;
	}
*/

/******************************************************************************/
/*                                  Indices                                   */
/******************************************************************************/


/** Table of Contents *********************************************************/

	.toc a {
		/* More spacing; use padding to make it part of the click target. */
		padding-top: 0.1rem;
		/* Larger, more consistently-sized click target */
		display: block;
		/* Reverse color scheme */
		color: black;
		border-color: #3980B5;
		border-bottom-width: 3px !important;
		margin-bottom: 0px !important;
	}
	.toc a:visited {
		border-color: #054572;
	}
	.toc a:not(:focus):not(:hover) {
		/* Allow colors to cascade through from link styling */
		border-bottom-color: transparent;
	}

	.toc, .toc ol, .toc ul, .toc li {
		list-style: none; /* Numbers must be inlined into source */
		/* because generated content isn't search/selectable and markers can't do multilevel yet */
		margin:  0;
		padding: 0;
		line-height: 1.1rem; /* consistent spacing */
	}

	/* ToC not indented until third level, but font style & margins show hierarchy */
	.toc > li             { font-weight: bold;   }
	.toc > li li          { font-weight: normal; }
	.toc > li li li       { font-size:   95%;    }
	.toc > li li li li    { font-size:   90%;    }
	.toc > li li li li .secno { font-size: 85%; }
	.toc > li li li li li { font-size:   85%;    }
	.toc > li li li li li .secno { font-size: 100%; }

	/* @supports not (display:grid) { */
		.toc > li             { margin: 1.5rem 0;    }
		.toc > li li          { margin: 0.3rem 0;    }
		.toc > li li li       { margin-left: 2rem;   }

		/* Section numbers in a column of their own */
		.toc .secno {
			float: left;
			width: 4rem;
			white-space: nowrap;
		}

		.toc li {
			clear: both;
		}

		:not(li) > .toc              { margin-left:  5rem; }
		.toc .secno                  { margin-left: -5rem; }
		.toc > li li li .secno       { margin-left: -7rem; }
		.toc > li li li li .secno    { margin-left: -9rem; }
		.toc > li li li li li .secno { margin-left: -11rem; }

		/* Tighten up indentation in narrow ToCs */
		@media (max-width: 30em) {
			:not(li) > .toc              { margin-left:  4rem; }
			.toc .secno                  { margin-left: -4rem; }
			.toc > li li li              { margin-left:  1rem; }
			.toc > li li li .secno       { margin-left: -5rem; }
			.toc > li li li li .secno    { margin-left: -6rem; }
			.toc > li li li li li .secno { margin-left: -7rem; }
		}
	/* } */

	@supports (display:grid) and (display:contents) {
		/* Use #toc over .toc to override non-@supports rules. */
		#toc {
			display: grid;
			align-content: start;
			grid-template-columns: auto 1fr;
			grid-column-gap: 1rem;
			column-gap: 1rem;
			grid-row-gap: .6rem;
			row-gap: .6rem;
		}
		#toc h2 {
			grid-column: 1 / -1;
			margin-bottom: 0;
		}
		#toc ol,
		#toc li,
		#toc a {
			display: contents;
			/* Switch <a> to subgrid when supported */
		}
		#toc span {
			margin: 0;
		}
		#toc > .toc > li > a > span {
			/* The spans of the top-level list,
			   comprising the first items of each top-level section. */
			margin-top: 1.1rem;
		}
		#toc#toc .secno { /* Ugh, need more specificity to override base.css */
			grid-column: 1;
			width: auto;
			margin-left: 0;
		}
		#toc .content {
			grid-column: 2;
			width: auto;
			margin-right: 1rem;
		}
		#toc .content:hover {
			background: rgba(75%, 75%, 75%, .25);
			border-bottom: 3px solid #054572;
			margin-bottom: -3px;
		}
		#toc li li li .content {
			margin-left: 1rem;
		}
		#toc li li li li .content {
			margin-left: 2rem;
		}
	}


/** Index *********************************************************************/

	/* Index Lists: Layout */
	ul.index       { margin-left: 0; columns: 15em; text-indent: 1em hanging; }
	ul.index li    { margin-left: 0; list-style: none; break-inside: avoid; }
	ul.index li li { margin-left: 1em }
	ul.index dl    { margin-top: 0; }
	ul.index dt    { margin: .2em 0 .2em 20px;}
	ul.index dd    { margin: .2em 0 .2em 40px;}
	/* Index Lists: Typography */
	ul.index ul,
	ul.index dl { font-size: smaller; }
	@media not print {
		ul.index li span {
			white-space: nowrap;
			color: transparent; }
		ul.index li a:hover + span,
		ul.index li a:focus + span {
			color: #707070;
		}
	}

/** Index Tables *****************************************************/
	/* See also the data table styling section, which this effectively subclasses */

	table.index {
		font-size: small;
		border-collapse: collapse;
		border-spacing: 0;
		text-align: left;
		margin: 1em 0;
	}

	table.index td,
	table.index th {
		padding: 0.4em;
	}

	table.index tr:hover td:not([rowspan]),
	table.index tr:hover th:not([rowspan]) {
		background: #f7f8f9;
	}

	/* The link in the first column in the property table (formerly a TD) */
	table.index th:first-child a {
		font-weight: bold;
	}

/******************************************************************************/
/*                                    Print                                   */
/******************************************************************************/

	@media print {
		/* Pages have their own margins. */
		html {
			margin: 0;
		}
		/* Serif for print. */
		body {
			font-family: serif;
		}
	}
	@page {
		margin: 1.5cm 1.1cm;
	}

/******************************************************************************/
/*                                    Legacy                                  */
/******************************************************************************/

	/* This rule is inherited from past style sheets. No idea what it's for. */
	.hide { display: none }



/******************************************************************************/
/*                             Overflow Control                               */
/******************************************************************************/

	.figure .caption, .sidefigure .caption, figcaption {
		/* in case figure is overlarge, limit caption to 50em */
		max-width: 50rem;
		margin-left: auto;
		margin-right: auto;
	}
	.overlarge {
		/* Magic to create good table positioning:
		   "content column" is 50ems wide at max; less on smaller screens.
		   Extra space (after ToC + content) is empty on the right.

		   1. When table < content column, centers table in column.
		   2. When content < table < available, left-aligns.
		   3. When table > available, fills available + scroll bar.
		*/ 
		display: grid;
		grid-template-columns: minmax(0, 50em);
	}
	.overlarge > table {
		/* limit preferred width of table */
		max-width: 50em;
		margin-left: auto;
		margin-right: auto;
	}

	@media (min-width: 55em) {
		.overlarge {
			margin-right: calc(13px + 26.5rem - 50vw);
			max-width: none;
		}
	}
	@media screen and (min-width: 78em) {
		body:not(.toc-inline) .overlarge {
			/* 30.5em body padding 50em content area */
			margin-right: calc(40em - 50vw) !important;
		}
	}
	@media screen and (min-width: 90em) {
		body:not(.toc-inline) .overlarge {
			/* 4em html margin 30.5em body padding 50em content area */
			margin-right: calc(84.5em - 100vw) !important;
		}
	}

	@media not print {
		.overlarge {
			overflow-x: auto;
			/* See Lea Verou's explanation background-attachment:
			 * http://lea.verou.me/2012/04/background-attachment-local/
			 *
			background: top left  / 4em 100% linear-gradient(to right,  #ffffff, rgba(255, 255, 255, 0)) local,
			            top right / 4em 100% linear-gradient(to left, #ffffff, rgba(255, 255, 255, 0)) local,
			            top left  / 1em 100% linear-gradient(to right,  #c3c3c5, rgba(195, 195, 197, 0)) scroll,
			            top right / 1em 100% linear-gradient(to left, #c3c3c5, rgba(195, 195, 197, 0)) scroll,
			            white;
			background-repeat: no-repeat;
			*/
		}
	}
</style>
  <link href="https://www.w3.org/StyleSheets/TR/2016/W3C-ED" rel="stylesheet">
  <link href="https://wicg.github.io/shape-detection-api" rel="canonical">
<style>
table {
  border-collapse: collapse;
  border-left-style: hidden;
  border-right-style: hidden;
  text-align: left;
}
table caption {
  font-weight: bold;
  padding: 3px;
  text-align: left;
}
table td, table th {
  border: 1px solid black;
  padding: 3px;
}
</style>
<style>/* style-md-lists */

/* This is a weird hack for me not yet following the commonmark spec
   regarding paragraph and lists. */
[data-md] > :first-child {
    margin-top: 0;
}
[data-md] > :last-child {
    margin-bottom: 0;
}</style>
<style>/* style-selflinks */

.heading, .issue, .note, .example, li, dt {
    position: relative;
}
a.self-link {
    position: absolute;
    top: 0;
    left: calc(-1 * (3.5rem - 26px));
    width: calc(3.5rem - 26px);
    height: 2em;
    text-align: center;
    border: none;
    transition: opacity .2s;
    opacity: .5;
}
a.self-link:hover {
    opacity: 1;
}
.heading > a.self-link {
    font-size: 83%;
}
li > a.self-link {
    left: calc(-1 * (3.5rem - 26px) - 2em);
}
dfn > a.self-link {
    top: auto;
    left: auto;
    opacity: 0;
    width: 1.5em;
    height: 1.5em;
    background: gray;
    color: white;
    font-style: normal;
    transition: opacity .2s, background-color .2s, color .2s;
}
dfn:hover > a.self-link {
    opacity: 1;
}
dfn > a.self-link:hover {
    color: black;
}

a.self-link::before            { content: "¶"; }
.heading > a.self-link::before { content: "§"; }
dfn > a.self-link::before      { content: "#"; }</style>
<style>/* style-counters */

body {
    counter-reset: example figure issue;
}
.issue {
    counter-increment: issue;
}
.issue:not(.no-marker)::before {
    content: "Issue " counter(issue);
}

.example {
    counter-increment: example;
}
.example:not(.no-marker)::before {
    content: "Example " counter(example);
}
.invalid.example:not(.no-marker)::before,
.illegal.example:not(.no-marker)::before {
    content: "Invalid Example" counter(example);
}

figcaption {
    counter-increment: figure;
}
figcaption:not(.no-marker)::before {
    content: "Figure " counter(figure) " ";
}</style>
<style>/* style-autolinks */

.css.css, .property.property, .descriptor.descriptor {
    color: #005a9c;
    font-size: inherit;
    font-family: inherit;
}
.css::before, .property::before, .descriptor::before {
    content: "‘";
}
.css::after, .property::after, .descriptor::after {
    content: "’";
}
.property, .descriptor {
    /* Don't wrap property and descriptor names */
    white-space: nowrap;
}
.type { /* CSS value <type> */
    font-style: italic;
}
pre .property::before, pre .property::after {
    content: "";
}
[data-link-type="property"]::before,
[data-link-type="propdesc"]::before,
[data-link-type="descriptor"]::before,
[data-link-type="value"]::before,
[data-link-type="function"]::before,
[data-link-type="at-rule"]::before,
[data-link-type="selector"]::before,
[data-link-type="maybe"]::before {
    content: "‘";
}
[data-link-type="property"]::after,
[data-link-type="propdesc"]::after,
[data-link-type="descriptor"]::after,
[data-link-type="value"]::after,
[data-link-type="function"]::after,
[data-link-type="at-rule"]::after,
[data-link-type="selector"]::after,
[data-link-type="maybe"]::after {
    content: "’";
}

[data-link-type].production::before,
[data-link-type].production::after,
.prod [data-link-type]::before,
.prod [data-link-type]::after {
    content: "";
}

[data-link-type=element],
[data-link-type=element-attr] {
    font-family: Menlo, Consolas, "DejaVu Sans Mono", monospace;
    font-size: .9em;
}
[data-link-type=element]::before { content: "<" }
[data-link-type=element]::after  { content: ">" }

[data-link-type=biblio] {
    white-space: pre;
}</style>
<style>/* style-dfn-panel */

.dfn-panel {
    position: absolute;
    z-index: 35;
    height: auto;
    width: -webkit-fit-content;
    width: fit-content;
    max-width: 300px;
    max-height: 500px;
    overflow: auto;
    padding: 0.5em 0.75em;
    font: small Helvetica Neue, sans-serif, Droid Sans Fallback;
    background: #DDDDDD;
    color: black;
    border: outset 0.2em;
}
.dfn-panel:not(.on) { display: none; }
.dfn-panel * { margin: 0; padding: 0; text-indent: 0; }
.dfn-panel > b { display: block; }
.dfn-panel a { color: black; }
.dfn-panel a:not(:hover) { text-decoration: none !important; border-bottom: none !important; }
.dfn-panel > b + b { margin-top: 0.25em; }
.dfn-panel ul { padding: 0; }
.dfn-panel li { list-style: inside; }
.dfn-panel.activated {
    display: inline-block;
    position: fixed;
    left: .5em;
    bottom: 2em;
    margin: 0 auto;
    max-width: calc(100vw - 1.5em - .4em - .5em);
    max-height: 30vh;
}

.dfn-paneled { cursor: pointer; }
</style>
<style>/* style-syntax-highlighting */
pre.idl.highlight { color: #708090; }
.highlight:not(.idl) { background: hsl(24, 20%, 95%); }
code.highlight { padding: .1em; border-radius: .3em; }
pre.highlight, pre > code.highlight { display: block; padding: 1em; margin: .5em 0; overflow: auto; border-radius: 0; }
c-[a] { color: #990055 } /* Keyword.Declaration */
c-[b] { color: #990055 } /* Keyword.Type */
c-[c] { color: #708090 } /* Comment */
c-[d] { color: #708090 } /* Comment.Multiline */
c-[e] { color: #0077aa } /* Name.Attribute */
c-[f] { color: #669900 } /* Name.Tag */
c-[g] { color: #222222 } /* Name.Variable */
c-[k] { color: #990055 } /* Keyword */
c-[l] { color: #000000 } /* Literal */
c-[m] { color: #000000 } /* Literal.Number */
c-[n] { color: #0077aa } /* Name */
c-[o] { color: #999999 } /* Operator */
c-[p] { color: #999999 } /* Punctuation */
c-[s] { color: #a67f59 } /* Literal.String */
c-[t] { color: #a67f59 } /* Literal.String.Single */
c-[u] { color: #a67f59 } /* Literal.String.Double */
c-[cp] { color: #708090 } /* Comment.Preproc */
c-[c1] { color: #708090 } /* Comment.Single */
c-[cs] { color: #708090 } /* Comment.Special */
c-[kc] { color: #990055 } /* Keyword.Constant */
c-[kn] { color: #990055 } /* Keyword.Namespace */
c-[kp] { color: #990055 } /* Keyword.Pseudo */
c-[kr] { color: #990055 } /* Keyword.Reserved */
c-[ld] { color: #000000 } /* Literal.Date */
c-[nc] { color: #0077aa } /* Name.Class */
c-[no] { color: #0077aa } /* Name.Constant */
c-[nd] { color: #0077aa } /* Name.Decorator */
c-[ni] { color: #0077aa } /* Name.Entity */
c-[ne] { color: #0077aa } /* Name.Exception */
c-[nf] { color: #0077aa } /* Name.Function */
c-[nl] { color: #0077aa } /* Name.Label */
c-[nn] { color: #0077aa } /* Name.Namespace */
c-[py] { color: #0077aa } /* Name.Property */
c-[ow] { color: #999999 } /* Operator.Word */
c-[mb] { color: #000000 } /* Literal.Number.Bin */
c-[mf] { color: #000000 } /* Literal.Number.Float */
c-[mh] { color: #000000 } /* Literal.Number.Hex */
c-[mi] { color: #000000 } /* Literal.Number.Integer */
c-[mo] { color: #000000 } /* Literal.Number.Oct */
c-[sb] { color: #a67f59 } /* Literal.String.Backtick */
c-[sc] { color: #a67f59 } /* Literal.String.Char */
c-[sd] { color: #a67f59 } /* Literal.String.Doc */
c-[se] { color: #a67f59 } /* Literal.String.Escape */
c-[sh] { color: #a67f59 } /* Literal.String.Heredoc */
c-[si] { color: #a67f59 } /* Literal.String.Interpol */
c-[sx] { color: #a67f59 } /* Literal.String.Other */
c-[sr] { color: #a67f59 } /* Literal.String.Regex */
c-[ss] { color: #a67f59 } /* Literal.String.Symbol */
c-[vc] { color: #0077aa } /* Name.Variable.Class */
c-[vg] { color: #0077aa } /* Name.Variable.Global */
c-[vi] { color: #0077aa } /* Name.Variable.Instance */
c-[il] { color: #000000 } /* Literal.Number.Integer.Long */
</style>
 <body class="h-entry">
  <div class="head">
   <p data-fill-with="logo"></p>
   <h1 class="p-name no-ref allcaps" id="title">加速的图形识别</h1>
   <h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Editor’s Draft, <time class="dt-updated" datetime="1970-01-01">1 January 1970</time></span></h2>
   <div data-fill-with="spec-metadata">
    <dl>
     <dt>This version:
     <dd><a class="u-url" href="https://wicg.github.io/shape-detection-api">https://wicg.github.io/shape-detection-api</a>
     <dt class="editor">Editor:
     <dd class="editor p-author h-card vcard" data-editor-id="82825"><a class="p-name fn u-email email" href="mailto:mcasas@google.com">Miguel Casas-Sanchez</a> (<span class="p-org org">Google Inc.</span>)
     <dt>Participate:
     <dd><a href="https://www.w3.org/community/wicg/">Join the W3C Community Group</a>
     <dd><a href="https://github.com/WICG/shape-detection-api">Fix the text through GitHub</a>
    </dl>
   </div>
   <div data-fill-with="warning"></div>
   <p class="copyright" data-fill-with="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 1970 the Contributors to the 加速的图形识别 Specification, published by the <a href="https://www.w3.org/community/wicg/">Web Platform Incubator Community Group</a> under the <a href="https://www.w3.org/community/about/agreements/cla/">W3C Community Contributor License Agreement (CLA)</a>.
A human-readable <a href="http://www.w3.org/community/about/agreements/cla-deed/">summary</a> is available. </p>
   <hr title="Separator for header">
  </div>
  <div class="p-summary" data-fill-with="abstract">
   <h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
   <p>本文档描述了一套Chrome中针对静态和/或动态图像的图形识别（如：人脸识别）API。</p>
  </div>
  <div data-fill-with="at-risk"></div>
  <h2 class="no-num no-toc no-ref heading settled" id="status"><span class="content">Status of this document</span></h2>
  <div data-fill-with="status">
   <p> This specification was published by the <a href="https://www.w3.org/community/wicg/">Web Platform Incubator Community Group</a>.
  It is not a W3C Standard nor is it on the W3C Standards Track.

  Please note that under the <a href="https://www.w3.org/community/about/agreements/cla/">W3C Community Contributor License Agreement (CLA)</a> there is a limited opt-out and other conditions apply.

  Learn more about <a href="http://www.w3.org/community/">W3C Community and Business Groups</a>. </p>
   <p></p>
  </div>
  <div data-fill-with="at-risk"></div>
  <nav data-fill-with="table-of-contents" id="toc">
   <h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
   <ol class="toc" role="directory">
    <li>
     <a href="#introduction"><span class="secno">1</span> <span class="content">简介</span></a>
     <ol class="toc">
      <li><a href="#image-sources-for-detection"><span class="secno">1.1</span> <span class="content">图形识别的场景</span></a>
     </ol>
    <li>
     <a href="#api"><span class="secno">2</span> <span class="content">图形识别API</span></a>
     <ol class="toc">
      <li><a href="#image-sources-for-detection①"><span class="secno">2.1</span> <span class="content">用于识别的图像源</span></a>
      <li><a href="#face-detection-api"><span class="secno">2.2</span> <span class="content">人脸识别API</span></a>
      <li><a href="#barcode-detection-api"><span class="secno">2.3</span> <span class="content">条形码识别API</span></a>
      <li><a href="#text-detection-api"><span class="secno">2.4</span> <span class="content">文本识别API</span></a>
     </ol>
    <li>
     <a href="#examples"><span class="secno">3</span> <span class="content">示例</span></a>
     <ol class="toc">
      <li><a href="#platform-support-for-a-given-detector"><span class="secno">3.1</span> <span class="content">图形识别器的平台支持</span></a>
      <li><a href="#face-detection"><span class="secno">3.2</span> <span class="content">人脸识别</span></a>
      <li><a href="#barcode-detection"><span class="secno">3.3</span> <span class="content">条形码识别</span></a>
      <li><a href="#text-detection"><span class="secno">3.4</span> <span class="content">文本识别</span></a>
     </ol>
    <li><a href="#conformance"><span class="secno"></span> <span class="content"> Conformance</span></a>
    <li>
     <a href="#index"><span class="secno"></span> <span class="content">Index</span></a>
     <ol class="toc">
      <li><a href="#index-defined-here"><span class="secno"></span> <span class="content">Terms defined by this specification</span></a>
      <li><a href="#index-defined-elsewhere"><span class="secno"></span> <span class="content">Terms defined by reference</span></a>
     </ol>
    <li>
     <a href="#references"><span class="secno"></span> <span class="content">References</span></a>
     <ol class="toc">
      <li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a>
     </ol>
    <li><a href="#idl-index"><span class="secno"></span> <span class="content">IDL Index</span></a>
   </ol>
  </nav>
  <main>
   <h2 class="heading settled" data-level="1" id="introduction"><span class="secno">1. </span><span class="content">简介</span><a class="self-link" href="#introduction"></a></h2>
   <p>照片和图像是互联网构成中最大的部分，其中相当一部分包含了可识别的特征，比如人脸，二维码或者文本。可想而之，识别这些特征的计算开销非常大，但有些很有趣场景，比如在照片中自动标记人脸，或者根据图像中的URL进行重定向。硬件厂商从很久以前就已经开始支持这些特性，但Web应用迟迟未能很好地利用上这些硬件特性，必须借助一些难用的程序库才能达到目的。</p>
   <h3 class="heading settled" data-level="1.1" id="image-sources-for-detection"><span class="secno">1.1. </span><span class="content">图形识别的场景</span><a class="self-link" href="#image-sources-for-detection"></a></h3>
   <p>请参考代码库中<a href="https://github.com/WICG/shape-detection-api/blob/gh-pages/README.md">自述/解释</a> 的文档。</p>
   <h2 class="heading settled" data-level="2" id="api"><span class="secno">2. </span><span class="content">图形识别API</span><a class="self-link" href="#api"></a></h2>
   <p>某些特定的浏览器可能会提供识别器来标示当前硬件是否提供加速功能。</p>
   <h3 class="heading settled" data-level="2.1" id="image-sources-for-detection①"><span class="secno">2.1. </span><span class="content">用于识别的图像源</span><a class="self-link" href="#image-sources-for-detection①"></a></h3>
   <p class="note" role="note"> 本节的灵感来自 <a href="https://www.w3.org/TR/2dcontext/#image-sources-for-2d-rendering-contexts">HTML Canvas 2D Context §image-sources-for-2d-rendering-contexts</a>。 </p>
   <p><code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource">ImageBitmapSource</a></code> 允许多种图形接口的实现对象作为图像源，进行识别处理。</p>
   <ul>
    <li data-md>
     <p>当<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①">ImageBitmapSource</a></code>对象代表<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/embedded-content.html#htmlimageelement" id="ref-for-htmlimageelement">HTMLImageElement</a></code>的时候，该元素的图像必须用作源图像。而在特定情况下，当<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource②">ImageBitmapSource</a></code>对象代表<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/embedded-content.html#htmlimageelement" id="ref-for-htmlimageelement①">HTMLImageElement</a></code>中的动画图像的时候，用户代理程序(User Agent)必须显示这个动画图像的默认图像（该默认图像指的是，在动画图像被禁用或不支持动画的环境下，需要展现的图像），或者没有默认图像的话，就显示该动画图像的第一帧。</p>
    <li data-md>
     <p>当<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource③">ImageBitmapSource</a></code>对象代表<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/media.html#htmlvideoelement" id="ref-for-htmlvideoelement">HTMLVideoElement</a></code>的时候，该视频播放的当前帧必须用作源图像，同时，该源图像的尺寸必须是视频源的<a href="https://drafts.csswg.org/css2/conform.html#intrinsic">固有维数(intrinsic dimensions)</a>，换句话说，就是视频源经过任意比例的调整后的大小。</p>
    <li data-md>
     <p>当<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource④">ImageBitmapSource</a></code>对象代表<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/canvas.html#htmlcanvaselement" id="ref-for-htmlcanvaselement">HTMLCanvasElement</a></code>的时候，该元素的位图必须用作源图像。</p>
   </ul>
   <p>当用户代理程序(User Agent)被要求用某种既有的<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource⑤">ImageBitmapSource</a></code>作为识别器的<code>detect()</code>方法的输入参数的时候，必须执行以下步骤：</p>
   <ul>
    <li data-md>
     <p>如果<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource⑥">ImageBitmapSource</a></code>所含的有效脚本源(<span spec-section="#concept-origin"></span>)和当前文档的有效脚本源不同，就拒绝对应的Promise对象，并附上一个名为<code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#securityerror" id="ref-for-securityerror">SecurityError</a></code>的新建<code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#idl-DOMException" id="ref-for-idl-DOMException">DOMException</a></code>对象。</p>
    <li data-md>
     <p>如果一个<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource⑦">ImageBitmapSource</a></code>是一个处于<var>broken</var>状态的<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/embedded-content.html#htmlimageelement" id="ref-for-htmlimageelement②">HTMLImageElement</a></code>对象的话，就拒绝对应的Promise对象，并附上一个名为<code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#invalidstateerror" id="ref-for-invalidstateerror">InvalidStateError</a></code>的新建<code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#idl-DOMException" id="ref-for-idl-DOMException①">DOMException</a></code>对象，同时停止之后的所有步骤。</p>
    <li data-md>
     <p>如果<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource⑧">ImageBitmapSource</a></code>是一个不能完整解码的<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/embedded-content.html#htmlimageelement" id="ref-for-htmlimageelement③">HTMLImageElement</a></code>对象的话，就拒绝对应的Promise对象，并附上一个名为<code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#invalidstateerror" id="ref-for-invalidstateerror①">InvalidStateError</a></code>的新建<code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#idl-DOMException" id="ref-for-idl-DOMException②">DOMException</a></code>对象，同时停止之后的所有步骤。</p>
    <li data-md>
     <p>如果一个<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource⑨">ImageBitmapSource</a></code>是一个<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/media.html#htmlvideoelement" id="ref-for-htmlvideoelement①">HTMLVideoElement</a></code>对象，且其<a href="https://html.spec.whatwg.org/multipage/embedded-content.html#ready-states:dom-media-readystate"><var>readyState</var></a>属性为<var>HAVE_NOTHING</var> 或 <var>HAVE_METADATA</var>的话，就拒绝对应的Promise对象，并附上一个名为<code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#invalidstateerror" id="ref-for-invalidstateerror②">InvalidStateError</a></code>的新建<code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#idl-DOMException" id="ref-for-idl-DOMException③">DOMException</a></code>对象，同时停止之后的所有步骤。</p>
    <li data-md>
     <p>如果一个<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①⓪">ImageBitmapSource</a></code>是一个<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/canvas.html#htmlcanvaselement" id="ref-for-htmlcanvaselement①">HTMLCanvasElement</a></code>对象，且其位图的<var>origin-clean</var> (<span spec-section="#concept-canvas-origin-clean"></span>)标识为false的话，就拒绝对应的Promise对象，并附上一个名为<code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#securityerror" id="ref-for-securityerror①">SecurityError</a></code>的新建<code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#idl-DOMException" id="ref-for-idl-DOMException④">DOMException</a></code>对象，同时停止之后的所有步骤。</p>
   </ul>
   <p>请注意，如果一个<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①①">ImageBitmapSource</a></code>的水平尺寸或垂直尺寸等于0，那么对应的Promise对象就会被简单地当作一个空的已检测对象序列来处理。</p>
   <h3 class="heading settled" data-level="2.2" id="face-detection-api"><span class="secno">2.2. </span><span class="content">人脸识别API</span><a class="self-link" href="#face-detection-api"></a></h3>
   <p><code class="idl"><a data-link-type="idl" href="#facedetector" id="ref-for-facedetector">FaceDetector</a></code>代表一个针对图像中的人脸进行识别的底层加速平台组件。创建时可以选择一个<code class="idl"><a data-link-type="idl" href="#dictdef-facedetectoroptions" id="ref-for-dictdef-facedetectoroptions">FaceDetectorOptions</a></code>的Dictionary对象作为入参。它提供了一个单独的 <code class="idl"><a data-link-type="idl" href="#dom-facedetector-detect" id="ref-for-dom-facedetector-detect">detect()</a></code>方法操作<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①②">ImageBitmapSource</a></code>对象，并返回Promise对象。如果检测到<a href="#image-sources-for-detection">§ 1.1 图形识别的场景</a>中提及的用例，则该方法必须拒绝该Promise对象；否则，它可能会向<code class="idl"><a data-link-type="idl" href="#detectedface" id="ref-for-detectedface">DetectedFace</a></code>序列推入一个新任务，这样会消耗操作系统或平台资源去依序处理该Promise，每个任务由一个<code class="idl"><a data-link-type="idl" href="#dom-detectedface-boundingbox" id="ref-for-dom-detectedface-boundingbox">boundingBox</a></code>所包含并界定。</p>
<pre class="idl highlight def"><c- b>dictionary</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="dictionary" data-export id="dictdef-facedetectoroptions"><code><c- g>FaceDetectorOptions</c-></code></dfn> {
  <a class="idl-code" data-link-type="interface" href="https://heycam.github.io/webidl/#idl-unsigned-short" id="ref-for-idl-unsigned-short"><c- b>unsigned</c-> <c- b>short</c-></a> <a class="idl-code" data-link-type="dict-member" data-type="unsigned short " href="#dom-facedetectoroptions-maxdetectedfaces" id="ref-for-dom-facedetectoroptions-maxdetectedfaces"><c- g>maxDetectedFaces</c-></a>;
  <a class="idl-code" data-link-type="interface" href="https://heycam.github.io/webidl/#idl-boolean" id="ref-for-idl-boolean"><c- b>boolean</c-></a> <a class="idl-code" data-link-type="dict-member" data-type="boolean " href="#dom-facedetectoroptions-fastmode" id="ref-for-dom-facedetectoroptions-fastmode"><c- g>fastMode</c-></a>;
};
</pre>
   <dl class="domintro">
    <dt><dfn class="dfn-paneled idl-code" data-dfn-for="FaceDetectorOptions" data-dfn-type="dict-member" data-export id="dom-facedetectoroptions-maxdetectedfaces"><code>maxDetectedFaces</code></dfn>, <span> of type <a data-link-type="idl-name" href="https://heycam.github.io/webidl/#idl-unsigned-short" id="ref-for-idl-unsigned-short①">unsigned short</a></span>
    <dd>当前场景中已识别的人脸数的最大值。
    <dt><dfn class="dfn-paneled idl-code" data-dfn-for="FaceDetectorOptions" data-dfn-type="dict-member" data-export id="dom-facedetectoroptions-fastmode"><code>fastMode</code></dfn>, <span> of type <a data-link-type="idl-name" href="https://heycam.github.io/webidl/#idl-boolean" id="ref-for-idl-boolean①">boolean</a></span>
    <dd>提示User Agent（UA）尝试以速度优先（于精确度）的模式，通过更小的比例尺（更靠近目标图形）或寻找更大的目标图形的办法进行识别。
   </dl>
<pre class="idl highlight def">[<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#Exposed" id="ref-for-Exposed"><c- g>Exposed</c-></a>=(<c- n>Window</c->,<c- n>Worker</c->), <a class="idl-code" data-link-type="constructor" href="#dom-facedetector-facedetector" id="ref-for-dom-facedetector-facedetector"><c- g>Constructor</c-></a>(<c- b>optional</c-> <a class="n" data-link-type="idl-name" href="#dictdef-facedetectoroptions" id="ref-for-dictdef-facedetectoroptions①"><c- n>FaceDetectorOptions</c-></a> <dfn class="idl-code" data-dfn-for="FaceDetector/FaceDetector(faceDetectorOptions)" data-dfn-type="argument" data-export id="dom-facedetector-facedetector-facedetectoroptions-facedetectoroptions"><code><c- g>faceDetectorOptions</c-></code><a class="self-link" href="#dom-facedetector-facedetector-facedetectoroptions-facedetectoroptions"></a></dfn>)]
<c- b>interface</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="interface" data-export id="facedetector"><code><c- g>FaceDetector</c-></code></dfn> {
  <c- b>Promise</c->&lt;<c- b>sequence</c->&lt;<a class="n" data-link-type="idl-name" href="#detectedface" id="ref-for-detectedface①"><c- n>DetectedFace</c-></a>>> <dfn class="dfn-paneled idl-code" data-dfn-for="FaceDetector" data-dfn-type="method" data-export data-lt="detect(image)" id="dom-facedetector-detect"><code><c- g>detect</c-></code></dfn>(<a class="n" data-link-type="idl-name" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①③"><c- n>ImageBitmapSource</c-></a> <dfn class="idl-code" data-dfn-for="FaceDetector/detect(image)" data-dfn-type="argument" data-export id="dom-facedetector-detect-image-image"><code><c- g>image</c-></code><a class="self-link" href="#dom-facedetector-detect-image-image"></a></dfn>);
};
</pre>
   <dl class="domintro">
    <dt><dfn class="dfn-paneled idl-code" data-dfn-for="FaceDetector" data-dfn-type="constructor" data-export data-lt="FaceDetector(faceDetectorOptions)|FaceDetector()" id="dom-facedetector-facedetector"><code>FaceDetector(optional FaceDetectorOptions faceDetectorOptions)</code></dfn>
    <dd>构建一个新的<code class="idl"><a data-link-type="idl" href="#facedetector" id="ref-for-facedetector①">FaceDetector</a></code>对象，附带可选项<var>faceDetectorOptions</var>。
    <dt><dfn class="idl-code" data-dfn-for="FaceDetector" data-dfn-type="method" data-export id="dom-facedetector-detect①"><code>detect()</code><a class="self-link" href="#dom-facedetector-detect①"></a></dfn>
    <dd>尝试在<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①④">ImageBitmapSource</a></code> |图像|中识别人脸，如果识别到人脸，则返回一个<code class="idl"><a data-link-type="idl" href="#detectedface" id="ref-for-detectedface②">DetectedFace</a></code>序列。
   </dl>
<pre class="idl highlight def"><c- b>interface</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="interface" data-export id="detectedface"><code><c- g>DetectedFace</c-></code></dfn> {
  [<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#SameObject" id="ref-for-SameObject"><c- g>SameObject</c-></a>] <c- b>readonly</c-> <c- b>attribute</c-> <a class="n" data-link-type="idl-name" href="https://drafts.fxtf.org/geometry-1/#domrectreadonly" id="ref-for-domrectreadonly"><c- n>DOMRectReadOnly</c-></a> <a class="idl-code" data-link-type="attribute" data-readonly data-type="DOMRectReadOnly" href="#dom-detectedface-boundingbox" id="ref-for-dom-detectedface-boundingbox①"><c- g>boundingBox</c-></a>;
};
</pre>
   <dl class="domintro">
    <dt><dfn class="dfn-paneled idl-code" data-dfn-for="DetectedFace" data-dfn-type="attribute" data-export id="dom-detectedface-boundingbox"><code>boundingBox</code></dfn>, <span> of type <a data-link-type="idl-name" href="https://drafts.fxtf.org/geometry-1/#domrectreadonly" id="ref-for-domrectreadonly①">DOMRectReadOnly</a>, readonly</span>
    <dd>与图像坐标轴对齐的一个矩形，该矩形标示了一个已识别特征的位置和范围。
   </dl>
   <div class="example" id="example-6b30fc23"><a class="self-link" href="#example-6b30fc23"></a> 人脸识别的实现案例有：<a href="https://developer.android.com/reference/android/media/FaceDetector.html">Android FaceDetector</a>, <a href="https://developer.apple.com/reference/coreimage/cifacefeature?language=objc">Apple’s CIFaceFeature</a> 或者 <a href="https://msdn.microsoft.com/library/windows/apps/windows.media.faceanalysis.facedetector.aspx">Windows 10 FaceDetector</a>。 </div>
   <div class="note" role="note">
     Consider adding attributes such as, e.g.: 
<pre>[SameObject] readonly attribute unsigned long id;
[SameObject] readonly attribute FrozenArray&lt;Landmark>? landmarks;
</pre>
    <p>to <code class="idl"><a data-link-type="idl" href="#detectedface" id="ref-for-detectedface③">DetectedFace</a></code>.</p>
   </div>
   <h3 class="heading settled" data-level="2.3" id="barcode-detection-api"><span class="secno">2.3. </span><span class="content">条形码识别API</span><a class="self-link" href="#barcode-detection-api"></a></h3>
   <p><code class="idl"><a data-link-type="idl" href="#barcodedetector" id="ref-for-barcodedetector">BarcodeDetector</a></code>代表一个针对图像中的二维码或条形码进行识别的底层加速平台组件。它提供了一个单独的<code class="idl"><a data-link-type="idl" href="#dom-barcodedetector-detect" id="ref-for-dom-barcodedetector-detect">detect()</a></code>方法操作<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①⑤">ImageBitmapSource</a></code>对象，并返回Promise对象。如果检测到<a href="#image-sources-for-detection">§ 1.1 图形识别的场景</a>中提及的情况，则该方法必须拒绝该Promise对象；否则，它可能会向<code class="idl"><a data-link-type="idl" href="#detectedbarcode" id="ref-for-detectedbarcode">DetectedBarcode</a></code>序列推入一个新任务，这样会消耗操作系统或平台资源去依序处理该Promise。基本上每个任务包含<code class="idl"><a data-link-type="idl" href="#dom-detectedbarcode-boundingbox" id="ref-for-dom-detectedbarcode-boundingbox">boundingBox</a></code>和一系列<code class="idl"><a data-link-type="idl" href="https://w3c.github.io/mediacapture-image/#Point2D" id="ref-for-Point2D">Point2D</a></code>，甚至可能还有个解码后的<code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#idl-DOMString" id="ref-for-idl-DOMString">DOMString</a></code>对象<code class="idl"><a data-link-type="idl" href="#dom-detectedbarcode-rawvalue" id="ref-for-dom-detectedbarcode-rawvalue">rawValue</a></code>，由它们来确定边界。</p>
<pre class="idl highlight def">[<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#Exposed" id="ref-for-Exposed①"><c- g>Exposed</c-></a>=(<c- n>Window</c->,<c- n>Worker</c->), <dfn class="idl-code" data-dfn-for="BarcodeDetector" data-dfn-type="constructor" data-export data-lt="BarcodeDetector()" id="dom-barcodedetector-barcodedetector"><code><c- g>Constructor</c-></code><a class="self-link" href="#dom-barcodedetector-barcodedetector"></a></dfn>()]
<c- b>interface</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="interface" data-export id="barcodedetector"><code><c- g>BarcodeDetector</c-></code></dfn> {
  <c- b>Promise</c->&lt;<c- b>sequence</c->&lt;<a class="n" data-link-type="idl-name" href="#detectedbarcode" id="ref-for-detectedbarcode①"><c- n>DetectedBarcode</c-></a>>> <a class="idl-code" data-link-type="method" href="#dom-barcodedetector-detect" id="ref-for-dom-barcodedetector-detect①"><c- g>detect</c-></a>(<a class="n" data-link-type="idl-name" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①⑥"><c- n>ImageBitmapSource</c-></a> <dfn class="idl-code" data-dfn-for="BarcodeDetector/detect(image)" data-dfn-type="argument" data-export id="dom-barcodedetector-detect-image-image"><code><c- g>image</c-></code><a class="self-link" href="#dom-barcodedetector-detect-image-image"></a></dfn>);
};
</pre>
   <dl class="domintro">
    <dt><dfn class="dfn-paneled idl-code" data-dfn-for="BarcodeDetector" data-dfn-type="method" data-export data-lt="detect(image)" id="dom-barcodedetector-detect"><code>detect(ImageBitmapSource image)</code></dfn>
    <dd>尝试在<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①⑦">ImageBitmapSource</a></code>图像中识别条形码。
   </dl>
<pre class="idl highlight def"><c- b>interface</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="interface" data-export id="detectedbarcode"><code><c- g>DetectedBarcode</c-></code></dfn> {
  [<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#SameObject" id="ref-for-SameObject①"><c- g>SameObject</c-></a>] <c- b>readonly</c-> <c- b>attribute</c-> <a class="n" data-link-type="idl-name" href="https://drafts.fxtf.org/geometry-1/#domrectreadonly" id="ref-for-domrectreadonly②"><c- n>DOMRectReadOnly</c-></a> <a class="idl-code" data-link-type="attribute" data-readonly data-type="DOMRectReadOnly" href="#dom-detectedbarcode-boundingbox" id="ref-for-dom-detectedbarcode-boundingbox①"><c- g>boundingBox</c-></a>;
  [<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#SameObject" id="ref-for-SameObject②"><c- g>SameObject</c-></a>] <c- b>readonly</c-> <c- b>attribute</c-> <a class="idl-code" data-link-type="interface" href="https://heycam.github.io/webidl/#idl-DOMString" id="ref-for-idl-DOMString①"><c- b>DOMString</c-></a> <a class="idl-code" data-link-type="attribute" data-readonly data-type="DOMString" href="#dom-detectedbarcode-rawvalue" id="ref-for-dom-detectedbarcode-rawvalue①"><c- g>rawValue</c-></a>;
  [<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#SameObject" id="ref-for-SameObject③"><c- g>SameObject</c-></a>] <c- b>readonly</c-> <c- b>attribute</c-> <c- b>FrozenArray</c->&lt;<a class="n" data-link-type="idl-name" href="https://w3c.github.io/mediacapture-image/#Point2D" id="ref-for-Point2D①"><c- n>Point2D</c-></a>> <a class="idl-code" data-link-type="attribute" data-readonly data-type="FrozenArray<Point2D>" href="#dom-detectedbarcode-cornerpoints" id="ref-for-dom-detectedbarcode-cornerpoints"><c- g>cornerPoints</c-></a>;
};
</pre>
   <dl class="domintro">
    <dt><dfn class="dfn-paneled idl-code" data-dfn-for="DetectedBarcode" data-dfn-type="attribute" data-export id="dom-detectedbarcode-boundingbox"><code>boundingBox</code></dfn>, <span> of type <a data-link-type="idl-name" href="https://drafts.fxtf.org/geometry-1/#domrectreadonly" id="ref-for-domrectreadonly③">DOMRectReadOnly</a>, readonly</span>
    <dd>与图像坐标轴对齐的一个矩形，该矩形标示了一个已识别特征的位置和范围。
    <dt><dfn class="dfn-paneled idl-code" data-dfn-for="DetectedBarcode" data-dfn-type="attribute" data-export id="dom-detectedbarcode-rawvalue"><code>rawValue</code></dfn>, <span> of type <a data-link-type="idl-name" href="https://heycam.github.io/webidl/#idl-DOMString" id="ref-for-idl-DOMString②">DOMString</a>, readonly</span>
    <dd>从条形码解码得到的DOMString对象，该值可能为多行。
    <dt><dfn class="dfn-paneled idl-code" data-dfn-for="DetectedBarcode" data-dfn-type="attribute" data-export id="dom-detectedbarcode-cornerpoints"><code>cornerPoints</code></dfn>, <span> of type FrozenArray&lt;<a data-link-type="idl-name" href="https://w3c.github.io/mediacapture-image/#Point2D" id="ref-for-Point2D②">Point2D</a>>, readonly</span>
    <dd>一串已识别条形码的顶点序列（<a data-link-type="dfn" href="https://heycam.github.io/webidl/#idl-sequence" id="ref-for-idl-sequence">sequence</a>），顺序从左上角开始，以顺时针方向排列。因为现实中透视形变的原因，该序列不一定表示的是正方形。
   </dl>
   <div class="example" id="example-4de80147"><a class="self-link" href="#example-4de80147"></a> 实现了条形码/二维码识别的示例有：<a href="https://developers.google.com/android/reference/com/google/android/gms/vision/barcode/package-summary">Google Play Services</a> 或者 <a href="https://developer.apple.com/reference/coreimage/ciqrcodefeature?language=objc">Apple’s CICRCodeFeature</a>. </div>
   <h3 class="heading settled" data-level="2.4" id="text-detection-api"><span class="secno">2.4. </span><span class="content">文本识别API</span><a class="self-link" href="#text-detection-api"></a></h3>
   <p>TextDetector代表一个针对图像中的文本进行识别的底层加速平台组件。它提供了一个单独的<code class="idl"><a data-link-type="idl" href="#dom-textdetector-detect" id="ref-for-dom-textdetector-detect">detect()</a></code>方法操作<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①⑧">ImageBitmapSource</a></code>对象，并返回Promise对象。如果检测到<a href="#image-sources-for-detection">§ 1.1 图形识别的场景</a>中提及的情况，则该方法必须拒绝该Promise对象；否则，它可能会向<code class="idl"><a data-link-type="idl" href="#detectedtext" id="ref-for-detectedtext">DetectedText</a></code>序列推入一个新任务，这样会消耗操作系统或平台资源去依序处理该Promise，基本上每个task包含一个<code class="idl"><a data-link-type="idl" href="#dom-detectedtext-rawvalue" id="ref-for-dom-detectedtext-rawvalue">rawValue</a></code>，并由一个<code class="idl"><a data-link-type="idl" href="#dom-detectedtext-boundingbox" id="ref-for-dom-detectedtext-boundingbox">boundingBox</a></code>来确定边界。</p>
<pre class="idl highlight def">[
    <dfn class="idl-code" data-dfn-for="TextDetector" data-dfn-type="constructor" data-export data-lt="TextDetector()" id="dom-textdetector-textdetector"><code><c- g>Constructor</c-></code><a class="self-link" href="#dom-textdetector-textdetector"></a></dfn>,
    <a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#Exposed" id="ref-for-Exposed②"><c- g>Exposed</c-></a>=(<c- n>Window</c->,<c- n>Worker</c->),
] <c- b>interface</c-> <dfn class="idl-code" data-dfn-type="interface" data-export id="textdetector"><code><c- g>TextDetector</c-></code><a class="self-link" href="#textdetector"></a></dfn> {
    <c- b>Promise</c->&lt;<c- b>sequence</c->&lt;<a class="n" data-link-type="idl-name" href="#detectedtext" id="ref-for-detectedtext①"><c- n>DetectedText</c-></a>>> <a class="idl-code" data-link-type="method" href="#dom-textdetector-detect" id="ref-for-dom-textdetector-detect①"><c- g>detect</c-></a>(<a class="n" data-link-type="idl-name" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①⑨"><c- n>ImageBitmapSource</c-></a> <dfn class="idl-code" data-dfn-for="TextDetector/detect(image)" data-dfn-type="argument" data-export id="dom-textdetector-detect-image-image"><code><c- g>image</c-></code><a class="self-link" href="#dom-textdetector-detect-image-image"></a></dfn>);
};
</pre>
   <dl class="domintro">
    <dt><dfn class="dfn-paneled idl-code" data-dfn-for="TextDetector" data-dfn-type="method" data-export data-lt="detect(image)" id="dom-textdetector-detect"><code>detect(ImageBitmapSource image)</code></dfn>
    <dd>尝试在<code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource②⓪">ImageBitmapSource</a></code> |图像|中识别文本块。.
   </dl>
<pre class="idl highlight def">[
    <dfn class="idl-code" data-dfn-for="DetectedText" data-dfn-type="constructor" data-export data-lt="DetectedText()" id="dom-detectedtext-detectedtext"><code><c- g>Constructor</c-></code><a class="self-link" href="#dom-detectedtext-detectedtext"></a></dfn>,
] <c- b>interface</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="interface" data-export id="detectedtext"><code><c- g>DetectedText</c-></code></dfn> {
    [<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#SameObject" id="ref-for-SameObject④"><c- g>SameObject</c-></a>] <c- b>readonly</c-> <c- b>attribute</c-> <a class="n" data-link-type="idl-name" href="https://drafts.fxtf.org/geometry-1/#domrect" id="ref-for-domrect"><c- n>DOMRect</c-></a> <a class="idl-code" data-link-type="attribute" data-readonly data-type="DOMRect" href="#dom-detectedtext-boundingbox" id="ref-for-dom-detectedtext-boundingbox①"><c- g>boundingBox</c-></a>;
    [<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#SameObject" id="ref-for-SameObject⑤"><c- g>SameObject</c-></a>] <c- b>readonly</c-> <c- b>attribute</c-> <a class="idl-code" data-link-type="interface" href="https://heycam.github.io/webidl/#idl-DOMString" id="ref-for-idl-DOMString③"><c- b>DOMString</c-></a> <a class="idl-code" data-link-type="attribute" data-readonly data-type="DOMString" href="#dom-detectedtext-rawvalue" id="ref-for-dom-detectedtext-rawvalue①"><c- g>rawValue</c-></a>;
};
</pre>
   <dl class="domintro">
    <dt><dfn class="dfn-paneled idl-code" data-dfn-for="DetectedText" data-dfn-type="attribute" data-export id="dom-detectedtext-boundingbox"><code>boundingBox</code></dfn>, <span> of type <a data-link-type="idl-name" href="https://drafts.fxtf.org/geometry-1/#domrect" id="ref-for-domrect①">DOMRect</a>, readonly</span>
    <dd>与图像坐标轴对齐的一个矩形，该矩形标示了一个已识别特征的位置和范围。
    <dt><dfn class="dfn-paneled idl-code" data-dfn-for="DetectedText" data-dfn-type="attribute" data-export id="dom-detectedtext-rawvalue"><code>rawValue</code></dfn>, <span> of type <a data-link-type="idl-name" href="https://heycam.github.io/webidl/#idl-DOMString" id="ref-for-idl-DOMString④">DOMString</a>, readonly</span>
    <dd>从图像中识别到的原始字符串。
   </dl>
   <div class="example" id="example-dbd1d9dd"><a class="self-link" href="#example-dbd1d9dd"></a> 实现了文本识别的示例有：<a href="https://developers.google.com/android/reference/com/google/android/gms/vision/text/package-summary">Google Play Services</a>, <a href="https://developer.apple.com/reference/coreimage/cidetectortypetext">Apple’s CIDetector</a> 或者 <a href="https://msdn.microsoft.com/en-us/library/windows/apps/windows.media.ocr.aspx">Windows 10 <abbr title="Optical Character Recognition">OCR</abbr> API</a>. </div>
   <h2 class="heading settled" data-level="3" id="examples"><span class="secno">3. </span><span class="content">示例</span><a class="self-link" href="#examples"></a></h2>
   <p class="note" role="note"> 以下示例的微调或扩展版本，以及更多示例请参考<a href="https://codepen.io/collection/DwWVJj/">这个codepen集合</a>。 </p>
   <h3 class="heading settled" data-level="3.1" id="platform-support-for-a-given-detector"><span class="secno">3.1. </span><span class="content">图形识别器的平台支持</span><a class="self-link" href="#platform-support-for-a-given-detector"></a></h3>
   <div class="note" role="note"> 以下的示例同样可以在<a href="https://codepen.io/miguelao/pen/PbYpMv?editors=0010">这个codepen</a>中找到微调的版本。 </div>
   <div class="example" id="example-ab8de879">
    <a class="self-link" href="#example-ab8de879"></a> 
<pre class="highlight"><c- k>if</c-> <c- p>(</c->window<c- p>.</c->FaceDetector <c- o>==</c-> <c- kc>undefined</c-><c- p>)</c-> <c- p>{</c->
  console<c- p>.</c->error<c- p>(</c-><c- t>'Face Detection not supported on this platform'</c-><c- p>);</c->
<c- p>}</c->
<c- k>if</c-> <c- p>(</c->window<c- p>.</c->BarcodeDetector <c- o>==</c-> <c- kc>undefined</c-><c- p>)</c-> <c- p>{</c->
  console<c- p>.</c->error<c- p>(</c-><c- t>'Barcode Detection not supported on this platform'</c-><c- p>);</c->
<c- p>}</c->
<c- k>if</c-> <c- p>(</c->window<c- p>.</c->TextDetector <c- o>==</c-> <c- kc>undefined</c-><c- p>)</c-> <c- p>{</c->
  console<c- p>.</c->error<c- p>(</c-><c- t>'Text Detection not supported on this platform'</c-><c- p>);</c->
<c- p>}</c->
</pre>
   </div>
   <h3 class="heading settled" data-level="3.2" id="face-detection"><span class="secno">3.2. </span><span class="content">人脸识别</span><a class="self-link" href="#face-detection"></a></h3>
   <div class="note" role="note"> 以下的示例同样可以在<a href="https://codepen.io/miguelao/pen/YGrYAm?editors=0010">这个codepen</a>(或者<a href="https://codepen.io/miguelao/pen/ORYbbm?editors=0010">这个有边界框覆盖的图像示例中</a>)找到。 </div>
   <div class="example" id="example-0c908620">
    <a class="self-link" href="#example-0c908620"></a> 
<pre class="highlight"><c- a>let</c-> faceDetector <c- o>=</c-> <c- k>new</c-> FaceDetector<c- p>({</c->fastMode<c- o>:</c-> <c- kc>true</c-><c- p>,</c-> maxDetectedFaces<c- o>:</c-> <c- mi>1</c-><c- p>});</c->
<c- c1>// Assuming |theImage| is e.g. a &lt;img> content, or a Blob.</c->

faceDetector<c- p>.</c->detect<c- p>(</c->theImage<c- p>)</c->
<c- p>.</c->then<c- p>(</c->detectedFaces <c- p>=></c-> <c- p>{</c->
  <c- k>for</c-> <c- p>(</c-><c- kr>const</c-> face <c- k>of</c-> detectedFaces<c- p>)</c-> <c- p>{</c->
    console<c- p>.</c->log<c- p>(</c-><c- t>' Face @ (${face.boundingBox.x}, ${face.boundingBox.y}),'</c-> <c- o>+</c->
        <c- t>' size ${face.boundingBox.width}x${face.boundingBox.height}'</c-><c- p>);</c->
  <c- p>}</c->
<c- p>}).</c-><c- k>catch</c-><c- p>(()</c-> <c- p>=></c-> <c- p>{</c->
  console<c- p>.</c->error<c- p>(</c-><c- u>"Face Detection failed, boo."</c-><c- p>);</c->
<c- p>})</c->
</pre>
   </div>
   <h3 class="heading settled" data-level="3.3" id="barcode-detection"><span class="secno">3.3. </span><span class="content">条形码识别</span><a class="self-link" href="#barcode-detection"></a></h3>
   <div class="note" role="note"> 以下的示例同样可以在这个<a href="https://codepen.io/miguelao/pen/ZBBxOM?editors=0010">这个codepen</a>(或者<a href="https://codepen.io/miguelao/pen/bBWOzM?editors=0010">这个覆盖了边界框的图像示例中</a>)找到。 </div>
   <div class="example" id="example-0be05266">
    <a class="self-link" href="#example-0be05266"></a> 
<pre class="highlight"><c- a>let</c-> barcodeDetector <c- o>=</c-> <c- k>new</c-> BarcodeDetector<c- p>();</c->
<c- c1>// Assuming |theImage| is e.g. a &lt;img> content, or a Blob.</c->

barcodeDetector<c- p>.</c->detect<c- p>(</c->theImage<c- p>)</c->
<c- p>.</c->then<c- p>(</c->detectedCodes <c- p>=></c-> <c- p>{</c->
  <c- k>for</c-> <c- p>(</c-><c- kr>const</c-> barcode <c- k>of</c-> detectedCodes<c- p>)</c-> <c- p>{</c->
    console<c- p>.</c->log<c- p>(</c-><c- t>' Barcode ${barcode.rawValue}'</c-> <c- o>+</c->
        <c- t>' @ (${barcode.boundingBox.x}, ${barcode.boundingBox.y}) with size'</c-> <c- o>+</c->
        <c- t>' ${barcode.boundingBox.width}x${barcode.boundingBox.height}'</c-><c- p>);</c->
  <c- p>}</c->
<c- p>}).</c-><c- k>catch</c-><c- p>(()</c-> <c- p>=></c-> <c- p>{</c->
  console<c- p>.</c->error<c- p>(</c-><c- u>"Barcode Detection failed, boo."</c-><c- p>);</c->
<c- p>})</c->
</pre>
   </div>
   <h3 class="heading settled" data-level="3.4" id="text-detection"><span class="secno">3.4. </span><span class="content">文本识别</span><a class="self-link" href="#text-detection"></a></h3>
   <div class="note" role="note"> 以下的示例同样可以在<a href="http://s.codepen.io/xianglu_google/debug/pNGBKv">这个codepen</a> (或者<a href="https://codepen.io/miguelao/pen/VPMxrj">这个集成了视频捕捉功能的示例</a>)找到。 </div>
   <div class="example" id="example-4b69a955">
    <a class="self-link" href="#example-4b69a955"></a> 
<pre class="highlight"><c- a>let</c-> textDetector <c- o>=</c-> <c- k>new</c-> TextDetector<c- p>();</c->
<c- c1>// Assuming |theImage| is e.g. a &lt;img> content, or a Blob.</c->

textDetector<c- p>.</c->detect<c- p>(</c->theImage<c- p>)</c->
<c- p>.</c->then<c- p>(</c->detectedTextBlocks <c- p>=></c-> <c- p>{</c->
  <c- k>for</c-> <c- p>(</c-><c- kr>const</c-> textBlock <c- k>of</c-> detectedTextBlocks<c- p>)</c-> <c- p>{</c->
    console<c- p>.</c->log<c- p>(</c->
        <c- t>'text @ (${textBlock.boundingBox.x}, ${textBlock.boundingBox.y}), '</c-> <c- o>+</c->
        <c- t>'size ${textBlock.boundingBox.width}x${textBlock.boundingBox.height}'</c-><c- p>);</c->
  <c- p>}</c->
<c- p>}).</c-><c- k>catch</c-><c- p>(()</c-> <c- p>=></c-> <c- p>{</c->
  console<c- p>.</c->error<c- p>(</c-><c- u>"Text Detection failed, boo."</c-><c- p>);</c->
<c- p>})</c->
</pre>
   </div>
  </main>
  <div data-fill-with="conformance">
   <h2 class="no-ref no-num heading settled" id="conformance"><span class="content"> Conformance</span><a class="self-link" href="#conformance"></a></h2>
   <p> Conformance requirements are expressed with a combination of descriptive assertions and RFC 2119 terminology.
            The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL”
            in the normative parts of this document
            are to be interpreted as described in RFC 2119.
            However, for readability,
            these words do not appear in all uppercase letters in this specification. </p>
   <p> All of the text of this specification is normative
            except sections explicitly marked as non-normative, examples, and notes. <a data-link-type="biblio" href="#biblio-rfc2119">[RFC2119]</a> </p>
   <p> Examples in this specification are introduced with the words “for example”
            or are set apart from the normative text with <code>class="example"</code>, like this: </p>
   <div class="example" id="example-example"><a class="self-link" href="#example-example"></a> This is an example of an informative example. </div>
   <p> Informative notes begin with the word “Note”
            and are set apart from the normative text with <code>class="note"</code>, like this: </p>
   <p class="note" role="note"> Note, this is an informative note. </p>
  </div>
<script>
(function() {
  "use strict";
  var collapseSidebarText = '<span aria-hidden="true">←</span> '
                          + '<span>Collapse Sidebar</span>';
  var expandSidebarText   = '<span aria-hidden="true">→</span> '
                          + '<span>Pop Out Sidebar</span>';
  var tocJumpText         = '<span aria-hidden="true">↑</span> '
                          + '<span>Jump to Table of Contents</span>';

  var sidebarMedia = window.matchMedia('screen and (min-width: 78em)');
  var autoToggle   = function(e){ toggleSidebar(e.matches) };
  if(sidebarMedia.addListener) {
    sidebarMedia.addListener(autoToggle);
  }

  function toggleSidebar(on) {
    if (on == undefined) {
      on = !document.body.classList.contains('toc-sidebar');
    }

    /* Don’t scroll to compensate for the ToC if we’re above it already. */
    var headY = 0;
    var head = document.querySelector('.head');
    if (head) {
      // terrible approx of "top of ToC"
      headY += head.offsetTop + head.offsetHeight;
    }
    var skipScroll = window.scrollY < headY;

    var toggle = document.getElementById('toc-toggle');
    var tocNav = document.getElementById('toc');
    if (on) {
      var tocHeight = tocNav.offsetHeight;
      document.body.classList.add('toc-sidebar');
      document.body.classList.remove('toc-inline');
      toggle.innerHTML = collapseSidebarText;
      if (!skipScroll) {
        window.scrollBy(0, 0 - tocHeight);
      }
      tocNav.focus();
      sidebarMedia.addListener(autoToggle); // auto-collapse when out of room
    }
    else {
      document.body.classList.add('toc-inline');
      document.body.classList.remove('toc-sidebar');
      toggle.innerHTML = expandSidebarText;
      if (!skipScroll) {
        window.scrollBy(0, tocNav.offsetHeight);
      }
      if (toggle.matches(':hover')) {
        /* Unfocus button when not using keyboard navigation,
           because I don’t know where else to send the focus. */
        toggle.blur();
      }
    }
  }

  function createSidebarToggle() {
    /* Create the sidebar toggle in JS; it shouldn’t exist when JS is off. */
    var toggle = document.createElement('a');
      /* This should probably be a button, but appearance isn’t standards-track.*/
    toggle.id = 'toc-toggle';
    toggle.class = 'toc-toggle';
    toggle.href = '#toc';
    toggle.innerHTML = collapseSidebarText;

    sidebarMedia.addListener(autoToggle);
    var toggler = function(e) {
      e.preventDefault();
      sidebarMedia.removeListener(autoToggle); // persist explicit off states
      toggleSidebar();
      return false;
    }
    toggle.addEventListener('click', toggler, false);


    /* Get <nav id=toc-nav>, or make it if we don’t have one. */
    var tocNav = document.getElementById('toc-nav');
    if (!tocNav) {
      tocNav = document.createElement('p');
      tocNav.id = 'toc-nav';
      /* Prepend for better keyboard navigation */
      document.body.insertBefore(tocNav, document.body.firstChild);
    }
    /* While we’re at it, make sure we have a Jump to Toc link. */
    var tocJump = document.getElementById('toc-jump');
    if (!tocJump) {
      tocJump = document.createElement('a');
      tocJump.id = 'toc-jump';
      tocJump.href = '#toc';
      tocJump.innerHTML = tocJumpText;
      tocNav.appendChild(tocJump);
    }

    tocNav.appendChild(toggle);
  }

  var toc = document.getElementById('toc');
  if (toc) {
    createSidebarToggle();
    toggleSidebar(sidebarMedia.matches);

    /* If the sidebar has been manually opened and is currently overlaying the text
       (window too small for the MQ to add the margin to body),
       then auto-close the sidebar once you click on something in there. */
    toc.addEventListener('click', function(e) {
      if(e.target.tagName.toLowerCase() == "a" && document.body.classList.contains('toc-sidebar') && !sidebarMedia.matches) {
        toggleSidebar(false);
      }
    }, false);
  }
  else {
    console.warn("Can’t find Table of Contents. Please use <nav id='toc'> around the ToC.");
  }

  /* Wrap tables in case they overflow */
  var tables = document.querySelectorAll(':not(.overlarge) > table.data, :not(.overlarge) > table.index');
  var numTables = tables.length;
  for (var i = 0; i < numTables; i++) {
    var table = tables[i];
    var wrapper = document.createElement('div');
    wrapper.className = 'overlarge';
    table.parentNode.insertBefore(wrapper, table);
    wrapper.appendChild(table);
  }

})();
</script>
  <h2 class="no-num no-ref heading settled" id="index"><span class="content">Index</span><a class="self-link" href="#index"></a></h2>
  <h3 class="no-num no-ref heading settled" id="index-defined-here"><span class="content">Terms defined by this specification</span><a class="self-link" href="#index-defined-here"></a></h3>
  <ul class="index">
   <li><a href="#barcodedetector">BarcodeDetector</a><span>, in §2.3</span>
   <li><a href="#dom-barcodedetector-barcodedetector">BarcodeDetector()</a><span>, in §2.3</span>
   <li>
    boundingBox
    <ul>
     <li><a href="#dom-detectedbarcode-boundingbox">attribute for DetectedBarcode</a><span>, in §2.3</span>
     <li><a href="#dom-detectedface-boundingbox">attribute for DetectedFace</a><span>, in §2.2</span>
     <li><a href="#dom-detectedtext-boundingbox">attribute for DetectedText</a><span>, in §2.4</span>
    </ul>
   <li><a href="#dom-detectedbarcode-cornerpoints">cornerPoints</a><span>, in §2.3</span>
   <li><a href="#dom-facedetector-detect①">detect()</a><span>, in §2.2</span>
   <li><a href="#detectedbarcode">DetectedBarcode</a><span>, in §2.3</span>
   <li><a href="#detectedface">DetectedFace</a><span>, in §2.2</span>
   <li><a href="#detectedtext">DetectedText</a><span>, in §2.4</span>
   <li><a href="#dom-detectedtext-detectedtext">DetectedText()</a><span>, in §2.4</span>
   <li>
    detect(image)
    <ul>
     <li><a href="#dom-barcodedetector-detect">method for BarcodeDetector</a><span>, in §2.3</span>
     <li><a href="#dom-facedetector-detect">method for FaceDetector</a><span>, in §2.2</span>
     <li><a href="#dom-textdetector-detect">method for TextDetector</a><span>, in §2.4</span>
    </ul>
   <li><a href="#facedetector">FaceDetector</a><span>, in §2.2</span>
   <li><a href="#dom-facedetector-facedetector">FaceDetector()</a><span>, in §2.2</span>
   <li><a href="#dom-facedetector-facedetector">FaceDetector(faceDetectorOptions)</a><span>, in §2.2</span>
   <li><a href="#dictdef-facedetectoroptions">FaceDetectorOptions</a><span>, in §2.2</span>
   <li><a href="#dom-facedetectoroptions-fastmode">fastMode</a><span>, in §2.2</span>
   <li><a href="#dom-facedetectoroptions-maxdetectedfaces">maxDetectedFaces</a><span>, in §2.2</span>
   <li>
    rawValue
    <ul>
     <li><a href="#dom-detectedbarcode-rawvalue">attribute for DetectedBarcode</a><span>, in §2.3</span>
     <li><a href="#dom-detectedtext-rawvalue">attribute for DetectedText</a><span>, in §2.4</span>
    </ul>
   <li><a href="#dom-textdetector-textdetector">TextDetector()</a><span>, in §2.4</span>
   <li><a href="#textdetector">TextDetector</a><span>, in §2.4</span>
  </ul>
  <aside class="dfn-panel" data-for="term-for-domrect">
   <a href="https://drafts.fxtf.org/geometry-1/#domrect">https://drafts.fxtf.org/geometry-1/#domrect</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-domrect">2.4. 文本识别API</a> <a href="#ref-for-domrect①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-domrectreadonly">
   <a href="https://drafts.fxtf.org/geometry-1/#domrectreadonly">https://drafts.fxtf.org/geometry-1/#domrectreadonly</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-domrectreadonly">2.2. 人脸识别API</a> <a href="#ref-for-domrectreadonly①">(2)</a>
    <li><a href="#ref-for-domrectreadonly②">2.3. 条形码识别API</a> <a href="#ref-for-domrectreadonly③">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-htmlcanvaselement">
   <a href="https://html.spec.whatwg.org/multipage/canvas.html#htmlcanvaselement">https://html.spec.whatwg.org/multipage/canvas.html#htmlcanvaselement</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-htmlcanvaselement">2.1. 用于识别的图像源</a> <a href="#ref-for-htmlcanvaselement①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-htmlimageelement">
   <a href="https://html.spec.whatwg.org/multipage/embedded-content.html#htmlimageelement">https://html.spec.whatwg.org/multipage/embedded-content.html#htmlimageelement</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-htmlimageelement">2.1. 用于识别的图像源</a> <a href="#ref-for-htmlimageelement①">(2)</a> <a href="#ref-for-htmlimageelement②">(3)</a> <a href="#ref-for-htmlimageelement③">(4)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-htmlvideoelement">
   <a href="https://html.spec.whatwg.org/multipage/media.html#htmlvideoelement">https://html.spec.whatwg.org/multipage/media.html#htmlvideoelement</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-htmlvideoelement">2.1. 用于识别的图像源</a> <a href="#ref-for-htmlvideoelement①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-imagebitmapsource">
   <a href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource">https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-imagebitmapsource">2.1. 用于识别的图像源</a> <a href="#ref-for-imagebitmapsource①">(2)</a> <a href="#ref-for-imagebitmapsource②">(3)</a> <a href="#ref-for-imagebitmapsource③">(4)</a> <a href="#ref-for-imagebitmapsource④">(5)</a> <a href="#ref-for-imagebitmapsource⑤">(6)</a> <a href="#ref-for-imagebitmapsource⑥">(7)</a> <a href="#ref-for-imagebitmapsource⑦">(8)</a> <a href="#ref-for-imagebitmapsource⑧">(9)</a> <a href="#ref-for-imagebitmapsource⑨">(10)</a> <a href="#ref-for-imagebitmapsource①⓪">(11)</a> <a href="#ref-for-imagebitmapsource①①">(12)</a>
    <li><a href="#ref-for-imagebitmapsource①②">2.2. 人脸识别API</a> <a href="#ref-for-imagebitmapsource①③">(2)</a> <a href="#ref-for-imagebitmapsource①④">(3)</a>
    <li><a href="#ref-for-imagebitmapsource①⑤">2.3. 条形码识别API</a> <a href="#ref-for-imagebitmapsource①⑥">(2)</a> <a href="#ref-for-imagebitmapsource①⑦">(3)</a>
    <li><a href="#ref-for-imagebitmapsource①⑧">2.4. 文本识别API</a> <a href="#ref-for-imagebitmapsource①⑨">(2)</a> <a href="#ref-for-imagebitmapsource②⓪">(3)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-idl-DOMException">
   <a href="https://heycam.github.io/webidl/#idl-DOMException">https://heycam.github.io/webidl/#idl-DOMException</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-idl-DOMException">2.1. 用于识别的图像源</a> <a href="#ref-for-idl-DOMException①">(2)</a> <a href="#ref-for-idl-DOMException②">(3)</a> <a href="#ref-for-idl-DOMException③">(4)</a> <a href="#ref-for-idl-DOMException④">(5)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-idl-DOMString">
   <a href="https://heycam.github.io/webidl/#idl-DOMString">https://heycam.github.io/webidl/#idl-DOMString</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-idl-DOMString">2.3. 条形码识别API</a> <a href="#ref-for-idl-DOMString①">(2)</a> <a href="#ref-for-idl-DOMString②">(3)</a>
    <li><a href="#ref-for-idl-DOMString③">2.4. 文本识别API</a> <a href="#ref-for-idl-DOMString④">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-Exposed">
   <a href="https://heycam.github.io/webidl/#Exposed">https://heycam.github.io/webidl/#Exposed</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-Exposed">2.2. 人脸识别API</a>
    <li><a href="#ref-for-Exposed①">2.3. 条形码识别API</a>
    <li><a href="#ref-for-Exposed②">2.4. 文本识别API</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-invalidstateerror">
   <a href="https://heycam.github.io/webidl/#invalidstateerror">https://heycam.github.io/webidl/#invalidstateerror</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-invalidstateerror">2.1. 用于识别的图像源</a> <a href="#ref-for-invalidstateerror①">(2)</a> <a href="#ref-for-invalidstateerror②">(3)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-SameObject">
   <a href="https://heycam.github.io/webidl/#SameObject">https://heycam.github.io/webidl/#SameObject</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-SameObject">2.2. 人脸识别API</a>
    <li><a href="#ref-for-SameObject①">2.3. 条形码识别API</a> <a href="#ref-for-SameObject②">(2)</a> <a href="#ref-for-SameObject③">(3)</a>
    <li><a href="#ref-for-SameObject④">2.4. 文本识别API</a> <a href="#ref-for-SameObject⑤">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-securityerror">
   <a href="https://heycam.github.io/webidl/#securityerror">https://heycam.github.io/webidl/#securityerror</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-securityerror">2.1. 用于识别的图像源</a> <a href="#ref-for-securityerror①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-idl-boolean">
   <a href="https://heycam.github.io/webidl/#idl-boolean">https://heycam.github.io/webidl/#idl-boolean</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-idl-boolean">2.2. 人脸识别API</a> <a href="#ref-for-idl-boolean①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-idl-sequence">
   <a href="https://heycam.github.io/webidl/#idl-sequence">https://heycam.github.io/webidl/#idl-sequence</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-idl-sequence">2.3. 条形码识别API</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-idl-unsigned-short">
   <a href="https://heycam.github.io/webidl/#idl-unsigned-short">https://heycam.github.io/webidl/#idl-unsigned-short</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-idl-unsigned-short">2.2. 人脸识别API</a> <a href="#ref-for-idl-unsigned-short①">(2)</a>
   </ul>
  </aside>
  <h3 class="no-num no-ref heading settled" id="index-defined-elsewhere"><span class="content">Terms defined by reference</span><a class="self-link" href="#index-defined-elsewhere"></a></h3>
  <ul class="index">
   <li>
    <a data-link-type="biblio">[geometry-1]</a> defines the following terms:
    <ul>
     <li><span class="dfn-paneled" id="term-for-domrect" style="color:initial">DOMRect</span>
     <li><span class="dfn-paneled" id="term-for-domrectreadonly" style="color:initial">DOMRectReadOnly</span>
    </ul>
   <li>
    <a data-link-type="biblio">[HTML]</a> defines the following terms:
    <ul>
     <li><span class="dfn-paneled" id="term-for-htmlcanvaselement" style="color:initial">HTMLCanvasElement</span>
     <li><span class="dfn-paneled" id="term-for-htmlimageelement" style="color:initial">HTMLImageElement</span>
     <li><span class="dfn-paneled" id="term-for-htmlvideoelement" style="color:initial">HTMLVideoElement</span>
     <li><span class="dfn-paneled" id="term-for-imagebitmapsource" style="color:initial">ImageBitmapSource</span>
    </ul>
   <li>
    <a data-link-type="biblio">[WebIDL]</a> defines the following terms:
    <ul>
     <li><span class="dfn-paneled" id="term-for-idl-DOMException" style="color:initial">DOMException</span>
     <li><span class="dfn-paneled" id="term-for-idl-DOMString" style="color:initial">DOMString</span>
     <li><span class="dfn-paneled" id="term-for-Exposed" style="color:initial">Exposed</span>
     <li><span class="dfn-paneled" id="term-for-invalidstateerror" style="color:initial">InvalidStateError</span>
     <li><span class="dfn-paneled" id="term-for-SameObject" style="color:initial">SameObject</span>
     <li><span class="dfn-paneled" id="term-for-securityerror" style="color:initial">SecurityError</span>
     <li><span class="dfn-paneled" id="term-for-idl-boolean" style="color:initial">boolean</span>
     <li><span class="dfn-paneled" id="term-for-idl-sequence" style="color:initial">sequence</span>
     <li><span class="dfn-paneled" id="term-for-idl-unsigned-short" style="color:initial">unsigned short</span>
    </ul>
  </ul>
  <h2 class="no-num no-ref heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
  <h3 class="no-num no-ref heading settled" id="normative"><span class="content">Normative References</span><a class="self-link" href="#normative"></a></h3>
  <dl>
   <dt id="biblio-geometry-1">[GEOMETRY-1]
   <dd>Simon Pieters; Chris Harrelson. <a href="https://www.w3.org/TR/geometry-1/">Geometry Interfaces Module Level 1</a>. 4 December 2018. CR. URL: <a href="https://www.w3.org/TR/geometry-1/">https://www.w3.org/TR/geometry-1/</a>
   <dt id="biblio-html">[HTML]
   <dd>Anne van Kesteren; et al. <a href="https://html.spec.whatwg.org/multipage/">HTML Standard</a>. Living Standard. URL: <a href="https://html.spec.whatwg.org/multipage/">https://html.spec.whatwg.org/multipage/</a>
   <dt id="biblio-rfc2119">[RFC2119]
   <dd>S. Bradner. <a href="https://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a>. March 1997. Best Current Practice. URL: <a href="https://tools.ietf.org/html/rfc2119">https://tools.ietf.org/html/rfc2119</a>
   <dt id="biblio-webidl">[WebIDL]
   <dd>Boris Zbarsky. <a href="https://heycam.github.io/webidl/">Web IDL</a>. 15 December 2016. ED. URL: <a href="https://heycam.github.io/webidl/">https://heycam.github.io/webidl/</a>
  </dl>
  <h2 class="no-num no-ref heading settled" id="idl-index"><span class="content">IDL Index</span><a class="self-link" href="#idl-index"></a></h2>
<pre class="idl highlight def"><c- b>dictionary</c-> <a href="#dictdef-facedetectoroptions"><code><c- g>FaceDetectorOptions</c-></code></a> {
  <a class="idl-code" data-link-type="interface" href="https://heycam.github.io/webidl/#idl-unsigned-short" id="ref-for-idl-unsigned-short②"><c- b>unsigned</c-> <c- b>short</c-></a> <a class="idl-code" data-link-type="dict-member" data-type="unsigned short " href="#dom-facedetectoroptions-maxdetectedfaces" id="ref-for-dom-facedetectoroptions-maxdetectedfaces①"><c- g>maxDetectedFaces</c-></a>;
  <a class="idl-code" data-link-type="interface" href="https://heycam.github.io/webidl/#idl-boolean" id="ref-for-idl-boolean②"><c- b>boolean</c-></a> <a class="idl-code" data-link-type="dict-member" data-type="boolean " href="#dom-facedetectoroptions-fastmode" id="ref-for-dom-facedetectoroptions-fastmode①"><c- g>fastMode</c-></a>;
};

[<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#Exposed" id="ref-for-Exposed③"><c- g>Exposed</c-></a>=(<c- n>Window</c->,<c- n>Worker</c->), <a class="idl-code" data-link-type="constructor" href="#dom-facedetector-facedetector" id="ref-for-dom-facedetector-facedetector①"><c- g>Constructor</c-></a>(<c- b>optional</c-> <a class="n" data-link-type="idl-name" href="#dictdef-facedetectoroptions" id="ref-for-dictdef-facedetectoroptions①①"><c- n>FaceDetectorOptions</c-></a> <a href="#dom-facedetector-facedetector-facedetectoroptions-facedetectoroptions"><code><c- g>faceDetectorOptions</c-></code></a>)]
<c- b>interface</c-> <a href="#facedetector"><code><c- g>FaceDetector</c-></code></a> {
  <c- b>Promise</c->&lt;<c- b>sequence</c->&lt;<a class="n" data-link-type="idl-name" href="#detectedface" id="ref-for-detectedface①①"><c- n>DetectedFace</c-></a>>> <a href="#dom-facedetector-detect"><code><c- g>detect</c-></code></a>(<a class="n" data-link-type="idl-name" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①③①"><c- n>ImageBitmapSource</c-></a> <a href="#dom-facedetector-detect-image-image"><code><c- g>image</c-></code></a>);
};

<c- b>interface</c-> <a href="#detectedface"><code><c- g>DetectedFace</c-></code></a> {
  [<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#SameObject" id="ref-for-SameObject⑥"><c- g>SameObject</c-></a>] <c- b>readonly</c-> <c- b>attribute</c-> <a class="n" data-link-type="idl-name" href="https://drafts.fxtf.org/geometry-1/#domrectreadonly" id="ref-for-domrectreadonly④"><c- n>DOMRectReadOnly</c-></a> <a class="idl-code" data-link-type="attribute" data-readonly data-type="DOMRectReadOnly" href="#dom-detectedface-boundingbox" id="ref-for-dom-detectedface-boundingbox①①"><c- g>boundingBox</c-></a>;
};

[<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#Exposed" id="ref-for-Exposed①①"><c- g>Exposed</c-></a>=(<c- n>Window</c->,<c- n>Worker</c->), <a href="#dom-barcodedetector-barcodedetector"><code><c- g>Constructor</c-></code></a>()]
<c- b>interface</c-> <a href="#barcodedetector"><code><c- g>BarcodeDetector</c-></code></a> {
  <c- b>Promise</c->&lt;<c- b>sequence</c->&lt;<a class="n" data-link-type="idl-name" href="#detectedbarcode" id="ref-for-detectedbarcode①①"><c- n>DetectedBarcode</c-></a>>> <a class="idl-code" data-link-type="method" href="#dom-barcodedetector-detect" id="ref-for-dom-barcodedetector-detect①①"><c- g>detect</c-></a>(<a class="n" data-link-type="idl-name" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①⑥①"><c- n>ImageBitmapSource</c-></a> <a href="#dom-barcodedetector-detect-image-image"><code><c- g>image</c-></code></a>);
};

<c- b>interface</c-> <a href="#detectedbarcode"><code><c- g>DetectedBarcode</c-></code></a> {
  [<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#SameObject" id="ref-for-SameObject①①"><c- g>SameObject</c-></a>] <c- b>readonly</c-> <c- b>attribute</c-> <a class="n" data-link-type="idl-name" href="https://drafts.fxtf.org/geometry-1/#domrectreadonly" id="ref-for-domrectreadonly②①"><c- n>DOMRectReadOnly</c-></a> <a class="idl-code" data-link-type="attribute" data-readonly data-type="DOMRectReadOnly" href="#dom-detectedbarcode-boundingbox" id="ref-for-dom-detectedbarcode-boundingbox①①"><c- g>boundingBox</c-></a>;
  [<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#SameObject" id="ref-for-SameObject②①"><c- g>SameObject</c-></a>] <c- b>readonly</c-> <c- b>attribute</c-> <a class="idl-code" data-link-type="interface" href="https://heycam.github.io/webidl/#idl-DOMString" id="ref-for-idl-DOMString①①"><c- b>DOMString</c-></a> <a class="idl-code" data-link-type="attribute" data-readonly data-type="DOMString" href="#dom-detectedbarcode-rawvalue" id="ref-for-dom-detectedbarcode-rawvalue①①"><c- g>rawValue</c-></a>;
  [<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#SameObject" id="ref-for-SameObject③①"><c- g>SameObject</c-></a>] <c- b>readonly</c-> <c- b>attribute</c-> <c- b>FrozenArray</c->&lt;<a class="n" data-link-type="idl-name" href="https://w3c.github.io/mediacapture-image/#Point2D" id="ref-for-Point2D①①"><c- n>Point2D</c-></a>> <a class="idl-code" data-link-type="attribute" data-readonly data-type="FrozenArray<Point2D>" href="#dom-detectedbarcode-cornerpoints" id="ref-for-dom-detectedbarcode-cornerpoints①"><c- g>cornerPoints</c-></a>;
};

[
    <a href="#dom-textdetector-textdetector"><code><c- g>Constructor</c-></code></a>,
    <a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#Exposed" id="ref-for-Exposed②①"><c- g>Exposed</c-></a>=(<c- n>Window</c->,<c- n>Worker</c->),
] <c- b>interface</c-> <a href="#textdetector"><code><c- g>TextDetector</c-></code></a> {
    <c- b>Promise</c->&lt;<c- b>sequence</c->&lt;<a class="n" data-link-type="idl-name" href="#detectedtext" id="ref-for-detectedtext①①"><c- n>DetectedText</c-></a>>> <a class="idl-code" data-link-type="method" href="#dom-textdetector-detect" id="ref-for-dom-textdetector-detect①①"><c- g>detect</c-></a>(<a class="n" data-link-type="idl-name" href="https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmapsource" id="ref-for-imagebitmapsource①⑨①"><c- n>ImageBitmapSource</c-></a> <a href="#dom-textdetector-detect-image-image"><code><c- g>image</c-></code></a>);
};

[
    <a href="#dom-detectedtext-detectedtext"><code><c- g>Constructor</c-></code></a>,
] <c- b>interface</c-> <a href="#detectedtext"><code><c- g>DetectedText</c-></code></a> {
    [<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#SameObject" id="ref-for-SameObject④①"><c- g>SameObject</c-></a>] <c- b>readonly</c-> <c- b>attribute</c-> <a class="n" data-link-type="idl-name" href="https://drafts.fxtf.org/geometry-1/#domrect" id="ref-for-domrect②"><c- n>DOMRect</c-></a> <a class="idl-code" data-link-type="attribute" data-readonly data-type="DOMRect" href="#dom-detectedtext-boundingbox" id="ref-for-dom-detectedtext-boundingbox①①"><c- g>boundingBox</c-></a>;
    [<a class="idl-code" data-link-type="extended-attribute" href="https://heycam.github.io/webidl/#SameObject" id="ref-for-SameObject⑤①"><c- g>SameObject</c-></a>] <c- b>readonly</c-> <c- b>attribute</c-> <a class="idl-code" data-link-type="interface" href="https://heycam.github.io/webidl/#idl-DOMString" id="ref-for-idl-DOMString③①"><c- b>DOMString</c-></a> <a class="idl-code" data-link-type="attribute" data-readonly data-type="DOMString" href="#dom-detectedtext-rawvalue" id="ref-for-dom-detectedtext-rawvalue①①"><c- g>rawValue</c-></a>;
};

</pre>
  <aside class="dfn-panel" data-for="dictdef-facedetectoroptions">
   <b><a href="#dictdef-facedetectoroptions">#dictdef-facedetectoroptions</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dictdef-facedetectoroptions">2.2. 人脸识别API</a> <a href="#ref-for-dictdef-facedetectoroptions①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="dom-facedetectoroptions-maxdetectedfaces">
   <b><a href="#dom-facedetectoroptions-maxdetectedfaces">#dom-facedetectoroptions-maxdetectedfaces</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-facedetectoroptions-maxdetectedfaces">2.2. 人脸识别API</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="dom-facedetectoroptions-fastmode">
   <b><a href="#dom-facedetectoroptions-fastmode">#dom-facedetectoroptions-fastmode</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-facedetectoroptions-fastmode">2.2. 人脸识别API</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="facedetector">
   <b><a href="#facedetector">#facedetector</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-facedetector">2.2. 人脸识别API</a> <a href="#ref-for-facedetector①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="dom-facedetector-detect">
   <b><a href="#dom-facedetector-detect">#dom-facedetector-detect</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-facedetector-detect">2.2. 人脸识别API</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="dom-facedetector-facedetector">
   <b><a href="#dom-facedetector-facedetector">#dom-facedetector-facedetector</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-facedetector-facedetector">2.2. 人脸识别API</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="detectedface">
   <b><a href="#detectedface">#detectedface</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-detectedface">2.2. 人脸识别API</a> <a href="#ref-for-detectedface①">(2)</a> <a href="#ref-for-detectedface②">(3)</a> <a href="#ref-for-detectedface③">(4)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="dom-detectedface-boundingbox">
   <b><a href="#dom-detectedface-boundingbox">#dom-detectedface-boundingbox</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-detectedface-boundingbox">2.2. 人脸识别API</a> <a href="#ref-for-dom-detectedface-boundingbox①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="barcodedetector">
   <b><a href="#barcodedetector">#barcodedetector</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-barcodedetector">2.3. 条形码识别API</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="dom-barcodedetector-detect">
   <b><a href="#dom-barcodedetector-detect">#dom-barcodedetector-detect</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-barcodedetector-detect">2.3. 条形码识别API</a> <a href="#ref-for-dom-barcodedetector-detect①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="detectedbarcode">
   <b><a href="#detectedbarcode">#detectedbarcode</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-detectedbarcode">2.3. 条形码识别API</a> <a href="#ref-for-detectedbarcode①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="dom-detectedbarcode-boundingbox">
   <b><a href="#dom-detectedbarcode-boundingbox">#dom-detectedbarcode-boundingbox</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-detectedbarcode-boundingbox">2.3. 条形码识别API</a> <a href="#ref-for-dom-detectedbarcode-boundingbox①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="dom-detectedbarcode-rawvalue">
   <b><a href="#dom-detectedbarcode-rawvalue">#dom-detectedbarcode-rawvalue</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-detectedbarcode-rawvalue">2.3. 条形码识别API</a> <a href="#ref-for-dom-detectedbarcode-rawvalue①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="dom-detectedbarcode-cornerpoints">
   <b><a href="#dom-detectedbarcode-cornerpoints">#dom-detectedbarcode-cornerpoints</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-detectedbarcode-cornerpoints">2.3. 条形码识别API</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="dom-textdetector-detect">
   <b><a href="#dom-textdetector-detect">#dom-textdetector-detect</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-textdetector-detect">2.4. 文本识别API</a> <a href="#ref-for-dom-textdetector-detect①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="detectedtext">
   <b><a href="#detectedtext">#detectedtext</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-detectedtext">2.4. 文本识别API</a> <a href="#ref-for-detectedtext①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="dom-detectedtext-boundingbox">
   <b><a href="#dom-detectedtext-boundingbox">#dom-detectedtext-boundingbox</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-detectedtext-boundingbox">2.4. 文本识别API</a> <a href="#ref-for-dom-detectedtext-boundingbox①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="dom-detectedtext-rawvalue">
   <b><a href="#dom-detectedtext-rawvalue">#dom-detectedtext-rawvalue</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-detectedtext-rawvalue">2.4. 文本识别API</a> <a href="#ref-for-dom-detectedtext-rawvalue①">(2)</a>
   </ul>
  </aside>
<script>/* script-dfn-panel */

document.body.addEventListener("click", function(e) {
    var queryAll = function(sel) { return [].slice.call(document.querySelectorAll(sel)); }
    // Find the dfn element or panel, if any, that was clicked on.
    var el = e.target;
    var target;
    var hitALink = false;
    while(el.parentElement) {
        if(el.tagName == "A") {
            // Clicking on a link in a <dfn> shouldn't summon the panel
            hitALink = true;
        }
        if(el.classList.contains("dfn-paneled")) {
            target = "dfn";
            break;
        }
        if(el.classList.contains("dfn-panel")) {
            target = "dfn-panel";
            break;
        }
        el = el.parentElement;
    }
    if(target != "dfn-panel") {
        // Turn off any currently "on" or "activated" panels.
        queryAll(".dfn-panel.on, .dfn-panel.activated").forEach(function(el){
            el.classList.remove("on");
            el.classList.remove("activated");
        });
    }
    if(target == "dfn" && !hitALink) {
        // open the panel
        var dfnPanel = document.querySelector(".dfn-panel[data-for='" + el.id + "']");
        if(dfnPanel) {
            dfnPanel.classList.add("on");
            var rect = el.getBoundingClientRect();
            dfnPanel.style.left = window.scrollX + rect.right + 5 + "px";
            dfnPanel.style.top = window.scrollY + rect.top + "px";
            var panelRect = dfnPanel.getBoundingClientRect();
            var panelWidth = panelRect.right - panelRect.left;
            if(panelRect.right > document.body.scrollWidth && (rect.left - (panelWidth + 5)) > 0) {
                // Reposition, because the panel is overflowing
                dfnPanel.style.left = window.scrollX + rect.left - (panelWidth + 5) + "px";
            }
        } else {
            console.log("Couldn't find .dfn-panel[data-for='" + el.id + "']");
        }
    } else if(target == "dfn-panel") {
        // Switch it to "activated" state, which pins it.
        el.classList.add("activated");
        el.style.left = null;
        el.style.top = null;
    }

});
</script>